I am writing a thesis: Digital is better than analog

[RefD]

Ummm....Why is it that Digital is always trying to emulate Analog? I mean Analog is the perfect computer.

AUUGH!!

*uses tubemonkey35's head as a toilet plunger*

[tubemonkey35]

heheheh I found this old thread and could not resist.

I use both, so I'm just stirring poop up.

[Gentleman Jim]

MichaelAlan wrote:

An analog recording is one where the original sound signal is modulated onto another physical media or substrate such as the groove of a gramophone disc or the iron oxide surface of a magnetic tape. A physical quality in the medium (e.g., the intensity of the magnetic field or the path of a record groove) is directly related, or analogous, to the physical properties of the original sound (e.g., the amplitude, phase, etc.)

A digital recording is produced by converting the physical properties of the original sound into digital information (called bits), which can then be stored and played back for reproduction. The accuracy of the conversion process depends on the sampling rate (how often the sound is sampled) and the sampling depth (how much information each sample contains). However, unlike analog recording, the physical medium for storing digital samples becomes immaterial in recovery of the encoded information as long as the individual bits can be recovered.


Lactation describes the secretion of milk from the mammary glands, the process of providing that milk to the young, and the period of time that a mother lactates to feed her young. The process occurs in all female mammals, and in humans it is commonly referred to as breastfeeding or nursing. In most species milk comes out of the mother's nipples; however, the platypus (a non-placental mammal) releases milk through ducts in its abdomen. In only one species of mammal, the Dayak fruit bat, is milk production a normal male function. In some other mammals, the male may produce milk as the result of a hormone imbalance. This phenomenon may also be observed in newborn infants as well (for instance witch's milk).

Contents [hide]
1 Purpose
2 Human lactation
2.1 Hormonal influences
2.1.1 Lactogenesis I
2.1.2 Lactogenesis II
2.1.3 Lactogenesis III
2.2 Milk ejection reflex
2.3 Afterpains
2.4 Lactation without pregnancy
3 References
4 See also



[edit] Purpose
The chief function of lactation is to provide nutrition to the young after birth. In almost all mammals lactation, or more correctly the suckling stimulus, induces a period of infertility, usually by the suppression of ovulation, which serves to provide the optimal birth spacing for survival of the offspring.[1]


[edit] Human lactation

When the baby sucks its mother's breast, a hormone called oxytocin compels the milk to flow from the alveoli, through the ducts (milk canals) into the sacs (milk pools) behind the areola and then into the baby's mouth
[edit] Hormonal influences
From the fourth month of pregnancy (the second and third trimesters), a woman's body produces hormones that stimulate the growth of the milk duct system in the breasts:

Progesterone ? influences the growth in size of alveoli and lobes. Progesterone levels drop after birth. This triggers the onset of copious milk production.[2]
Estrogen ? stimulates the milk duct system to grow and become specific. Estrogen levels also drop at delivery and remain low for the first several months of breastfeeding.[2] It is recommended that breastfeeding mothers avoid estrogen-based birth control methods, as a spike in estrogen levels may reduce a mother's milk supply.
Follicle stimulating hormone (FSH)
Luteinizing hormone (LH)
Prolactin ? contributes to the increased growth of the alveoli during pregnancy.
Oxytocin ? contracts the smooth muscle of the uterus during and after birth, and during orgasm. After birth, oxytocin contracts the smooth muscle layer of band-like cells surrounding the alveoli to squeeze the newly-produced milk into the duct system. Oxytocin is necessary for the milk ejection reflex, or let-down to occur.
Human placental lactogen (HPL) ? From the second month of pregnancy, the placenta releases large amounts of HPL. This hormone appears to be instrumental in breast, nipple, and areola growth before birth.
By the fifth or sixth month of pregnancy, the breasts are ready to produce milk. It is also possible to induce lactation without pregnancy.


[edit] Lactogenesis I
During the latter part of pregnancy, the woman's breasts enter into the Lactogenesis I stage. This is when the breasts make colostrum (see below), a thick, sometimes yellowish fluid. At this stage, high levels of progesterone inhibit most milk production. It is not a medical concern if a pregnant woman leaks any colostrum before her baby's birth, nor is it an indication of future milk production.


[edit] Lactogenesis II
At birth, prolactin levels remain high, while the delivery of the placenta results in a sudden drop in progesterone, estrogen, and HPL levels. This abrupt withdrawal of progesterone in the presence of high prolactin levels stimulates the copious milk production of Lactogenesis II.

When the breast is stimulated, prolactin levels in the blood rise, peak in about 45 minutes, and return to the pre-breastfeeding state about three hours later. The release of prolactin triggers the cells in the alveoli to make milk. Prolactin also transfers to the breast milk. Some research indicates that prolactin in milk is higher at times of higher milk production, and lower when breasts are fuller, and that the highest levels tend to occur between 2 a.m. and 6 a.m.[3]

Other hormones?notably insulin, thyroxine, and cortisol?are also involved, but their roles are not yet well understood. Although biochemical markers indicate that Lactogenesis II begins about 30?40 hours after birth, mothers do not typically begin feeling increased breast fullness (the sensation of milk "coming in") until 50?73 hours (2?3 days) after birth.

Colostrum is the first milk a breastfed baby receives. It contains higher amounts of white blood cells and antibodies than mature milk, and is especially high in immunoglobulin A (IgA), which coats the lining of the baby's immature intestines, and helps to prevent germs from invading the baby's system. Secretory IgA also helps prevent food allergies.[4] Over the first two weeks after the birth, colostrum production slowly gives way to mature breast milk.[2]


[edit] Lactogenesis III
The hormonal endocrine control system drives milk production during pregnancy and the first few days after the birth. When the milk supply is more firmly established, autocrine (or local) control system begins. This stage is called Lactogenesis III

During this stage, the more that milk is removed from the breasts, the more the breast will produce milk.[5][6] Research also suggests that draining the breasts more fully also increases the rate of milk production.[7] Thus the milk supply is strongly influenced by how often the baby feeds and how well it is able to transfer milk from the breast. Low supply can often be traced to:

not feeding or pumping often enough
inability of the infant to transfer milk effectively caused by, among other things:
jaw or mouth structure deficits
poor latching technique
rare maternal endocrine disorders
hypoplastic breast tissue
a metabolic or digestive inability in the infant, making it unable to digest the milk it receives
inadequate calorie intake or malnutrition of the mother

[edit] Milk ejection reflex
The release of the hormone oxytocin leads to the milk ejection or let-down reflex. Oxytocin stimulates the muscles surrounding the breast to squeeze out the milk. Breastfeeding mothers describe the sensation differently. Some feel a slight tingling, others feel immense amounts of pressure or slight pain/discomfort, and still others do not feel anything different.

The let-down reflex is not always consistent, especially at first. The thought of breastfeeding or the sound of any baby can stimulate this reflex, causing unwanted leakage, or both breasts may give out milk when an infant is feeding from one breast. However, this and other problems often settle after two weeks of feeding. Stress or anxiety can cause difficulties with breastfeeding.

A poor milk ejection reflex can be due to sore or cracked nipples, separation from the infant, a history of breast surgery, or tissue damage from prior breast trauma. If a mother has trouble breastfeeding, different methods of assisting the milk ejection reflex may help. These include feeding in a familiar and comfortable location, massage of the breast or back, or warming the breast with a cloth or shower.


[edit] Afterpains
The surge of oxytocin that triggers the milk ejection reflex also causes the uterus to contract. During breastfeeding, mothers may feel these contractions as afterpains. These may range from period-like cramps to strong labour-like contractions and can be more severe with second and subsequent babies.[8]


[edit] Lactation without pregnancy
Women who have never been pregnant are sometimes able to induce enough lactation to breastfeed. This is called "induced lactation". A woman who has breastfed before and re-starts is said to "relactate". If the nipples are consistently stimulated by a breast pump or actual suckling, the breasts will eventually begin to produce enough milk to begin feeding a baby. Once established, lactation adjusts to demand. This is how some adoptive mothers, usually beginning with a supplemental nursing system or some other form of supplementation, can breastfeed.[9] There is thought to be little or no difference in milk composition whether lactation is induced or a result of pregnancy. Rare accounts of male lactation (as distinct from galactorrhea) exist in the medical literature.

Some drugs, primarily atypical antipsychotics such as Risperdal, may cause lactation in both women and men. Also, some couples may use lactation for sexual purposes.


[edit]

Accurate, high quality sound reproduction is possible with both analog and digital systems. The principal advantage that digital systems have over analog systems is lower costs for end users. With analog recordings, consumers must use high-quality playback equipment to accurately separate the signal from the background without picking up noise or distortion. With digital, only the signal is encoded, so playback equipment can be much less expensive for a given quality. (Incidentally this same principle applies to digital video and still photography.)

Imperfections in the mechanical performance of the analog equipment may cause distortions like wow, flutter, tape hiss or record surface noise. Some of these distortions can be prevented using timebase correction, as is done in VHS tapes, filtering or high-quality components. Time-instability in digital systems (jitter) also degrades system performance, which is why most use time-coding on the media itself to prevent it. Digital information can also be somewhat self-correcting. After a signal has been converted into a digital format, error-correcting codes (looking for particular types or sizes of digital bits & bytes, and 'correcting' if not found) helps to prevent data loss and/or corruption. This allows digital formats to have a higher resistance to media deterioration than analog formats. That is not to say poorly produced digital media are immune to data loss. Laser rot was most troublesome to the Laserdisc format, which used digital audio, and was caused by inadequate disc manufacture. There can occasionally be difficulties related to the use of consumer recordable/rewritable compact disc. This may be due to poor quality CD recorder drives or low quality discs.

Unlike analog dubs, digital copies and regenerations are exact clones. They can be made nearly infinitely without degradation, unless DRM restrictions apply or mastering errors occur. Digital systems have the ability for the same medium to be used with arbitrarily high or low quality encoding methods and number of channels or other content, unlike mechanically pre-fixed speed and channels of practically all analog systems.

There are also several advantages of digital systems that are not related to sound quality but are of practical value. Most digital media have non-sequential (random) access, due to their disk or memory-based nature. In production, this makes editing much easier. It also allows the listener greater flexibility when playing back recordings. Most digital systems also have the ability to encode non-audio information into the digital stream, such as information about the artist, track titles, etc.

Also, whereas digital formats retain a sample rate, analog does not.


[edit] Noise and distortion
In the process of recording, storing and playing back the original sound wave analogy (in the form of an electronic signal), it is unavoidable that some signal degradation will occur. This degradation is in the form of linear (changes to the amplitude or phase response within a specified passband) and non-linear errors (noise and distortion). Noise is unrelated in time to the original signal content, while distortion is in some way related in time to the original signal content.


[edit] Digital fundamentals
A digital recorder firstly requires the input of an analog signal; this signal may come directly from a microphone pre-amp, but any analog audio signal can be converted. Measurements of the signal intensity are then made at regular intervals (sampling) by the analog-to-digital converter. At each sampling point, the signal must be assigned a specific intensity from a set range of values (quantization). In doing this, the original sound wave can now be described using only numbers - as digital information. The number of the sample is an analog of time, and the magnitude of the sample is an analog of pressure at the microphone (Watkinson 1994). When the original signal is converted into binary numbers (1's and 0's, called 'bits') further additions of noise and distortion (in the form of digital errors) can be rejected at every stage of processing. Error correction coding, essential when transferring digital audio over noisy channels, helps to eliminate bit errors. When playing back a digital recording, the digital information is converted back into a continuous, analog signal by a digital-to-analog converter. This electronic signal is then amplified and converted back into a sound wave by a loudspeaker.


[edit] Noise performance
For electronic audio signals, sources of noise include (unavoidable) mechanical, electrical and thermal noise level in the recording and playback cycle (mechanical transducers (microphones, loudspeakers), amplifiers, recording equipment, mastering process, reproduction equipment, etc). Whether an audio signal is, at some stage, converted into a digital form will affect how much noise is added. The actual process of digital conversion will always add some noise, however small in intensity.

The amount of noise that a piece of audio equipment adds to the original signal can be quantified. Mathematically, this can be expressed by means of the signal to noise ratio (SNR). Sometimes the maximum possible dynamic range of the system is quoted instead. In a digital system, the number of bits with which a signal is allowed to have on quantization will have a bearing on the level of noise and distortion added to that signal. The 16-bit digital system of Red Book audio CD has 216= 65,536 possible signal amplitudes, theoretically allowing for a SNR of 98 dB (Sony Europe 2001) and dynamic range of 96 dB.

Note that a decibel is one-tenth of a Bel. It is a somewhat strange concept that characterizes the logarithmic nature of human senses. Now to make it more complex, the amplitudes discussed in this article are voltage levels. To convert a voltage level ratio to a Bel, simply divide them and calculate the logarithm to base 10. Then multiply by 10 to get decibels. Unfortunately, Ohm's Law comes into play; the power of the sound is approximately the square of the voltage level. The human hearing range is around 120 dB.
In order to meet the theoretical performance of a 16 bit digital system, for a 0.5 V peak to peak input line signal, a PCM (pulse code modulation) quantizer would require an equivalent minimum input sensitivity of just 7.629 microvolts. For an analog recorder, this is equivalent to a 15.3 ppm sensitivity by part of the whole recording system and medium. With digital systems, the quality of reproduction depends on the analog-to-digital and digital-to-analog conversion steps, and does not depend on the quality of the recording medium. Practical digital converters may show considerable deviation from ideal performance.

Typically anything below 14 bits can lead to reduced sound quality, with 80 dB of SNR considered as an informal "minimum" for Hi-Fi audio. However, it is uncommon to find digital media specified for less than 14 bits, except for older 12-bit PCM Camcorder audio (or DAT in long-play, 32khz mode) and the output from older or lower-cost computer software, sound cards/circuitry, consoles and games (typically 8 bit as a minimum and standard, though trick sample output methods for generally non-PCM hardware gave SNR performances closer to that of an ideal "6" or "4" bit PCM digital converter).


[edit] Digital dither
In digital recording, quantization of the original analog signal results in quantization noise. Unlike the noise floor in analog systems, quantization noise is non-random in nature, and is more audibly disturbing. Dithering can be used to hide quantization noise. Dither reduces the amount of low level distortion in digital recordings but increases the amount of background noise by a few dB. Early tests suggested that undithered 14 bit recording or 13 bit dithered recordings were suitable for high-quality FM radio broadcasting (Croll 1970).


[edit] Greater than 16 bits
Each additional quantization bit theoretically adds a notable 6 dB in possible dynamic range, e.g. 24 x 6 = 144 dB for 24 bit quantization, 126 dB for 21-bit, and 120 dB for 20-bit. 19 bits has been shown to be necessary to capture some high-quality signals for broadcast (Manson 1980). The benefits of using digital recorders with greater than 16 bit accuracy can be applied to the 16 bits of audio CD. This may be done using dither and noise shaping. More noise is present in recordings using noise shaping, but the noise is present in less audible frequency regions, thus improving the subjective dynamic range.

One aspect that may prevent the performance of practical digital systems from meeting their theoretical performance is jitter. This is caused by deviations in the sampling of the waveform from ideal performance, and is usually expressed as a time value. Random jitter alters the noise floor of the digital system. It has been shown that a random jitter of 5 ns (nanoseconds) may be significant for 16 bit digital systems (Rumsey & Watkinson 1995). Systems of greater than 16 bits need performances higher than this (lower jitter meaning levels less than 5 ns) to meet their theoretical noise floors. Audibility tests have shown that the detection threshold for random jitter in musical signals is several hundred nanoseconds [1].


[edit] Analog systems
Consumer analog cassette tapes may have a dynamic range of 60 to 70 dB. Analog FM broadcasts rarely have a dynamic range exceeding 50 dB. The dynamic range of a direct-cut vinyl record may surpass 70 dB. Analog studio master tapes using Dolby-A noise reduction can have a dynamic range of around 80 dB (Stark 1989).


[edit] Rumble
"Rumble" is a form of noise peculiar to turntables. Because of imperfections in the bearings of turntables, the platter tends to have a slight amount of motion other than just the desired rotation. That is, besides its rotation, the turntable surface also moves up-and-down and side-to-side slightly. This additional motion is added to the desired signal as noise, usually of very low frequencies, creating a "rumbling" sound during quiet passages. Very inexpensive turntables sometimes used ball bearings which are very likely to generate audible amounts of rumble. More expensive turntables tend to use massive sleeve bearings which are much less likely to generate offensive amounts of rumble. Increased turntable mass also tends to lead to reduced rumble. A good turntable should have rumble at least 60 dB below the specified output level from the pick-up (Driscoll 1980).


[edit] Wow and flutter
Wow and flutter are the result of imperfections in the mechanical performance of analog devices. Wow and flutter are most noticeable on signals which contain pure tones. As an example, 0.22% (rms) wow may be detectable by listeners with piano music, but this increases to 0.56% with jazz music. For LP records, the quality of the turntable will have a large effect on the level of wow and flutter. A good turntable will have wow and flutter values of less than 0.05%, which is the speed variation compared to the ideal value (Driscoll 1980).

The digital equivalent of flutter is periodic jitter, which is caused by instablities in the sample clock of the converter (Rumsey & Watkinson 1995). The sensitivity of the converter to periodic jitter depends on the design of the converter. Periodic jitter produces modulation noise. Practical research by Benjamin and Gannon involving listening tests found that the lowest level of jitter to be audible on test signals was 10 ns (rms). With music, no listeners in the tests found jitter audible at levels lower than 20 ns (Dunn 2003).


[edit] Frequency response
The frequency response of audio CD is sufficiently wide to cover the entire audible range, which roughly extends from 20 Hz to 20 kHz. Analog audio is unrestricted in its possible frequency response, but the limitations of the particular analog format will provide a cap.

For digital systems, the maximum audio frequency response is "hardcoded" by the sampling frequency. The choice of sampling rate used in a digital system is based on the Nyquist-Shannon sampling theorem. This states that a sampled signal can be reproduced exactly as long as it is sampled at a frequency greater than twice the bandwidth of the signal. Therefore a sampling rate of 40 kHz would be enough to capture all the information contained in a signal having frequency bandwidth up to 20 kHz. The difficulty arises in removing all the signal content above 20 kHz, and unless this is done, aliasing of these higher frequencies may occur. This is where these higher, inaudible frequencies alias to frequencies which are in the audible range. To prevent aliasing, it is not necessary to design a brick-wall filter - that is a filter which perfectly removes all frequency content above (or below) a certain range. Instead, a sampling rate is chosen above the theoretical requirement. This allows for a less severe filter to be used. In addition to this, other methods can be used to try and increase performance, for example, oversampling.

High quality open-reel tape frequency response can extend from 10 Hz to well above 200 kHz. The linearity of the response may be indicated by providing information on the level of the response relative to a reference frequency. For example, a system component may have a response given as 20 Hz to 20 kHz +/- 3 dB relative to 1 kHz. Large, sudden deviations in the amplitude of response at different frequencies will have phase shifts associated with them, which are very audible. Some analog tape manufacturers specify frequency responses up to 20 kHz, but these measurements may have been made at low signal levels (Stark 1989). High-quality metal-particle cassettes may have a response extending up to 14 kHz at full (0 dB) recording level (Stark 1989).

The frequency response for a conventional LP player might be 30 Hz - 20 kHz +/- 3 dB. Unlike the audio CD, vinyl records do not require a cut-off in response above 20 kHz. The low frequency response of vinyl records is restricted by rumble noise (described above). In comparison, the CD system offers a frequency response of 20 Hz - 20 kHz +/- 0.5 dB, with a superior dynamic range over the entire audible frequency spectrum (Sony Europe 2001).

With vinyl records, there will be some loss in fidelity on each playing of the disc. This is due to the wear of the stylus in contact with the record surface. A good quality stylus, matched with a correctly set up pick-up arm, should cause minimal surface wear. When a CD is played, there is no physical contact involved, and the data is read optically using a laser beam. Therefore no such media deterioration takes place, and the CD will, with proper care, sound the same every time it is played.


[edit] Sound quality

[edit] Subjective evaluation
Subjective evaluation attempts to measure how well an audio component performs according to the human ear. The most common form of subjective test is a listening test, where the audio component is simply used in the context in which it was designed for. This test is popular with hi-fi reviewers, where the component is used for a length of time by the reviewer who then will describe the performance in subjective terms. Common descriptions include whether the component has a 'bright' or 'dull' sound, or how well the component manages to present a 'spatial image'.

Another type of subjective test is done under more controlled conditions, and attempts to remove possible bias from listening tests. These sorts of tests are done with the component hidden from the listener, and are called blind tests. To prevent possible bias from the person running the test, the blind test may be done so that this person is also unaware of the component under test. This type of test is called a double-blind test. This sort of test is often used to evaluate the performance of digital audio codecs.

There are critics of double-blind tests who see them as not allowing the listener to feel fully relaxed when evaluating the system component, and can therefore not judge differences between different components as well as in sighted (non-blind) tests. Those who employ the double-blind testing method may try to reduce listener stress by allowing a certain amount of time for listener training (Borwick et al. 1994).


[edit] Early digital recordings
Early digital audio machines had disappointing results, with digital converters introducing errors that the ear could detect (Watkinson 1994). Record companies released their first LPs based on digital audio masters in the late 1970s. CDs became available in the early 1980s. At this time analog sound reproduction was a mature technology. Some recording engineers like Jack Renner of the Telarc record label produced digital recordings which were well-received by critics for their sound quality (Greenfield et al. 1986). Some analog recordings were remastered for CD, but problems were occasionally identified with these releases. For instance, violins that once sounded well-balanced on analog (vinyl) disc would sound too aggressive on CD. One explanation for this was that engineers had learned to place microphones in such a way as to improve fidelity when producing analog recordings. Due to the extra resolution of the audio CD, such techniques were no longer appropriate. Other faults in recordings were more noticeable, like background noise.


[edit] Higher sampling rates
CD quality audio is sampled at 44.1 kHz (Nyquist frequency = 22.05 kHz) and at 16 bits. Sampling the waveform at higher frequencies and allowing for a greater number of bits per sample allows noise and distortion to be reduced further. DAT can store audio at up to 48 kHz, while DVD-Audio can be 96 or 192 kHz and up to 24 bits resolution. With these higher sampling rates, signal information is captured above what is generally considered to be the human hearing range.

Work done in 1980 by Muraoka et al. (J.Audio Eng. Soc., Vol 29, pp2-9) showed that music signals with frequency components above 20 kHz were only distinguished from those without by a few of the 176 test subjects (Kaoru & Shogo 2001). Later papers, however, by a number of different authors, have led to a greater discussion of the value of recording frequencies above 20 kHz. Such research led some to the belief that capturing these ultrasonic sounds could have some audible benefit. Audible differences were reported between recordings with and without ultrasonic responses. Dunn (1998) examined the performance of digital converters in order to see if these differences in performance could be explained [2]. He did this by examining the band-limiting filters used in converters and looking the artifacts they introduce.

A perceptual study by Nishiguchi et al. (2004) concluded that no perceivable difference could be found between music signals with and without frequency components above 21 kHz. They were, however, unable to say whether or not some subjects could perceive a difference, and felt that further evaluation tests were necessary [3].


[edit] Super Audio CD and DVD Audio
The Super Audio CD (SACD) format was created by Sony and Philips, who were also the developers of the earlier standard audio CD format. SACD uses Direct Stream Digital, which works quite differently to the PCM format discussed in this article. Instead of using a greater number of bits depth and attempting to record a signal's precise amplitude for every sample cycle, a Direct Stream Digital recorder works by encoding a signal in a series of PWM pulses - and therefore strictly speaking an analogue signal - (of fixed amplitude but variable duration and timing). The competing DVD-Audio format uses standard, linear PCM at variable sampling rates and bit depths, which the very least match and usually greatly surpass those of a standard CD Audio (16 bits, 44.1 kHz).

A Direct Stream Digital (DSD) recorder uses an oversampling design and a process called sigma-delta modulation. The sample rate of the recorder is 64 times the Nyquist rate (44.1 kHz), at around 3 Mhz. The output from a DSD recorder alternates between levels representing 'on' and 'off' states, and is a binary signal (called a bitstream). The long-term average of this signal is proportional to the original signal. In principle, the retention of the bitstream in DSD allows the SACD player to use a basic DAC design which incorporates a low-order analog filter.

There are fundamental distortion mechanisms present in the conventional implementation of DSD (Hawksford 2001). Historically, state-of-the-art ADCs were based around sigma-delta modulation designs. Oversampling converters are frequently used in linear PCM formats, where the ADC output is subject to bandlimiting and dithering (Hawksford 1995). Many modern converters use oversampling and a multibit design.

In the popular Hi-Fi press, it has been suggested that linear PCM "creates [a] stress reaction in people", and that DSD "is the only digital recording system that does not [...] have these effects" (Hawksford 2001). A double-blind subjective test between high resolution linear PCM (DVD-Audio) and DSD did not reveal a statistically significant difference [4]. Listeners involved in this test noted their great difficulty in hearing any difference between the two formats.


[edit] Analog warmth
Some audio enthusiasts prefer the sound of vinyl records over that of CD, this despite the apparent technical advantages of the digital format. Founder and editor Harry Pearson of The Absolute Sound journal says that "LPs are decisively more musical. CDs drain the soul from music. The emotional involvement disappears" [5]. Dub producer Adrian Sherwood has similar feelings about the analog cassette tape, which he prefers because of its warm sound [6].

Those who favour the digital format point to the results of blind tests, which demonstrate the high performance possible with digital recorders [7], [8]. The assertion is that the 'analog sound' is more a product of analog format inaccuracies than anything else. One early supporter of digital audio was the classical conductor Herbert von Karajan, who said that digital recording was "definitely superior to any other form of recording we know".


[edit] Was it ever entirely analog or digital?
Complicating the discussion is that recording professionals often mix and match analog and digital techniques in the process of producing a recording. Analog signals can be subjected to digital signal processing or effects, and inversely digital signals are converted back to analog in equipment that can include analog steps such as vacuum tube amplification.

For modern recordings, the controversy between analog recording and digital recording is becoming moot. No matter what format the user uses, the recording probably was digital at several stages in its life. In case of video recordings it is moot for one other reason; whether the format is analog or digital, digital signal processing is likely to have been used in some stages of its life, such as digital timebase correction on playback.

Despite this some musical artists, such as Mission of Burma, still make it a point to record fully analog albums.


[edit] Hybrid systems
While the words analog audio usually imply that the sound is described using a continuous time, continuous amplitudes approach in both the media and the reproduction/recording systems, and the words digital audio imply a discrete time, discrete amplitudes approach, there are methods of encoding audio that fall somewhere between the two, e.g. continuous time, discrete levels and discrete time,continuous levels.

While not as common as "pure analog" or "pure digital" methods, these situations do occur in practice. Indeed, all analog systems show discrete (quantized) behaviour at the microscopic scale [9]. Digital systems may use techniques which emulate the behaviour of analog (continuous) systems, e.g. dither.

While vinyl records and common compact cassettes are analog media and use quasi-linear mechanical encoding methods (e.g. spiral groove depth, tape magnetic field strength) without noticeable quantization or aliasing, there are analog non-linear systems that exhibit effects similar to those encountered on digital ones, such as aliasing and "hard" dynamic floors (e.g. frequency modulated audio on VHS tapes, PWM encoded signals).

Although those "hybrid" techniques are usually more common in telecommunications systems than in consumer audio, their existence alone blurs the distinctive line between certain digital and analog systems, at least for what regards some of their alleged advantages or disadvantages.


[edit] See also
Audiophile
Audio quality measurement
Audio system measurements
History of sound recording
Psychoacoustics

[edit] References
Ashihara, K. et al (2005). "Detection threshold for distortions due to jitter on digital audio", Acoustical Science and Technology, Vol. 26 (2005) , No. 1 pp.50-54.
Blech, D. & Yang, M. (2004). "Perceptual Discrimination of Digital Coding Formats", Audio Engineering Society Convention Paper 6086, May 2004.
Borwick, J. et al (1994). The Loudspeaker and Headphone Handbook, 2nd edition. Edited by John Borwick, with specialist contributors. Section 11.7 'Experimental Procedure', by Floyd Toole, pages 481-488. Focal Press. ISBN 0 240 51371 1.
Croll, M. (1970). "Pulse Code Modulation for High Quality Sound Distribution: Quantizing Distortion at Very Low Signal Levels", Research Department Report No. 1970/18, BBC.
Driscoll, R. (1980). Practical Hi-Fi Sound, 'Analogue and digital', pages 61-64; 'The pick-up, arm and turntable', pages 79-82. Hamlyn. ISBN 0 600 34627 7.
Dunn, J. (1998). "The benefits of 96 kHz sampling rate formats for those who cannot hear above 20 kHz", Preprint 4734, presented at the 104th AES Convention, May 1998.
Dunn, J. (2003). "Measurement Techniques for Digital Audio", Audio Precision Application Note #5, Audio Precision.
Greenfield, E. et al. (1986). The Penguin Guide to Compact Discs, Cassettes and LPs, Penguin.
Ely, S. (1978). "Idle-channel noise in p.c.m. sound-signal systems". BBC Research Department, Engineering Division.
Hawksford, M.O.J. (1991). "Introduction to Digital Audio", Images of Audio, Proceedings of the 10th International AES Conference, London, September 1991.
Hawksford, M.O.J. (1995). "Bitstream versus PCM debate for high-density compact disc", ARA/Meridian web page, November 1995.
Hawksford, M.O.J. (2001). "SDM versus LPCM: The Debate Continues", 110th AES Convention, paper 5397.
Hicks, C. (1995). "The Application of Dither and Noise-Shaping to Nyquist-Rate Digital Audio: an Introduction", Communications and Signal Processing Group, Cambridge University Engineering Department, United Kingdom.
Kaoru, A. & Shogo, K. (2001). "Detection threshold for tones above 22 kHz", Audio Engineering Society Convention Paper 5401. Presented at the 110th Convention, 2001.
Lesurf, J. "Analog or Digital?", The Scots Guide to Electronics. Retrieved October 2007.
Libbey, T. "Digital versus analog: digital music on CD reigns as the industry standard", Omni, February 1995.
Lipshitz, S. "The Digital Challenge: A Report", The BAS Speaker, Aug-Sept 1984.
Liversidge, A. "Analog versus digital: has vinyl been wrongly dethroned by the music industry?", Omni, February 1995.
Sony Europe (2001). Digital Audio Technology 4th edn, edited by J. Maes & M. Vercammen. Focal Press.
Manson, W. (1980). "Digital Sound: studio signal coding resolution for broadcasting". BBC Research Department, Engineering Division.
Nishiguchi, T. et al. (2004). "Perceptual Discrimination between Musical Sounds with and without Very High Frequency Components", NHK Laboratories Note No. 486, NHK (Japan Broadcasting Corporation).
Paul, J. "Last night a mix tape saved my life", The Guardian, September 26, 2003.
Pohlmann, K. (2005). Principles of Digital Audio 5th edn, McGraw-Hill Comp.
Rathmell, J. et al. (1997) "TDFD-based Measurement of Analog-to-Digital Converter Nonlinearity", Journal of the Audio Engineering Society, Volume 45, Number 10, pp. 832-840; October 1997.
Rumsey, F. & Watkinson, J. (1995). The Digital Interface Handbook, 2nd edition. Sections 2.5 and 6. Pages 37 and 154-160. Focal Press.
Stark, C. (1989). Encyclop?dia Britannica, 15th edition, Volume 27, Macropaedia article 'Sound', section: 'High-fidelity concepts and systems', page 625.
Watkinson J. (1994). An Introduction to Digital Audio. Section 1.2 'What is digital audio?', page 3; Section 2.1 'What can we hear?', page 26. Focal Press. ISBN 0 240 51378 9.


Frank Zappa called nipples, nozzles.

In the anatomy of mammals, a nipple or mammary papilla is a small projection of skin containing the outlets for 15-20 lactiferous ducts arranged cylindrically around the tip. The skin of the nipple is rich in a supply of special nerves that are sensitive to certain stimuli. The physiological purpose of nipples is to deliver milk to the infant, produced in the female mammary glands during lactation. In the male, nipples are often not considered functional with regard to breastfeeding, although male lactation is possible. Mammalian infants have a rooting instinct for seeking the nipple, and a sucking instinct for extracting milk.

Mammals typically have an even number of nipples arranged around bilaterally. In the primitive mammals (monotremes such as the platypus), the mammary glands empty onto the skin without a nipple.

In human anatomy, the two nipples are located near the center of the breasts, surrounded by an area of sensitive, pigmented skin known as the areola. The pigments of the nipple and areola are brown eumelanin (a brown pigment) and to a greater extent pheomelanin (a red pigment). The nipple and areola of males and females can be erotic receptors, or considered sex organs. Stimulation or sexual arousal can cause the nipples to become erect, due to the release of the polypeptide neurotransmitter oxytocin. Breastfeeding or exposure to cold temperatures often has this effect as well.

The average projection and size of human female nipples is slightly more than 3/8 inches (0.4 in./10mm.) [1]. Pregnancy and nursing tend to increase nipple size somewhat, and this increase may remain permanently thereafter. Pregnancy also increases the pigmentation of the nipples. The erection of the nipple is partially due to the cylindrically arranged muscle cells found within it. In many women there are small bulges on the areola, which are called 'Montgomery bodies'.

Embryologically, nipples develop along the 'milk lines' which in humans extend from the axilla (armpit) down to the pubis (groin) on both sides. Most mammals develop multiple nipples along each milk line, with the total number approximating the maximum litter size, and half the total number (i.e. the number on one side) approximating the average litter size for that species. Most people develop two nipples (one on each breast) but some have supernumerary nipples. Occasionally, these have lactiferous glands attached.

Sometimes, babies (male or female) are born producing milk. This, called 'witch's milk', is caused by maternal estrogens acting on the baby and is quite normal. Witch's milk disappears after several days.


[edit] Nipples on male mammals
Starting at conception and lasting until about 14 weeks, all mammalian fetuses within the same species look the same, regardless of gender. After 14 weeks, genetically-male fetuses begin producing male hormones such as testosterone. As "female" is the "developmental default" for mammals, by 14 weeks, the nipples have already formed.

Most of the time, males' nipples don't change much past this point. However, some males develop a condition known as gynecomastia, in which the fatty tissue around and under the nipple develops into something similar to a female breast. For males who develop gynecomastia during puberty, it is said the effects are temporary unless they are obese. This may happen whenever the testosterone level drops because of medications

The breasts are modified sudoriferous (sweat) glands, producing milk in females.[1] Each breast has one nipple surrounded by the areola. The areola is colored from pink to dark brown and has several sebaceous glands. In females, the larger mammary glands within the breast produce the milk. They are distributed throughout the breast, with two-thirds of the tissue found within 30 mm of the base of the nipple.[2] These are drained to the nipple by between 4 and 18 lactiferous ducts, where each duct has its own opening. The network formed by these ducts is complex, like the tangled roots of a tree. It is not always arranged radially, and branches close to the nipple. The ducts near the nipple do not act as milk reservoirs; Ramsay et al. have shown that conventionally described lactiferous sinuses do not, in fact, exist.

The remainder of the breast is composed of connective tissue (collagen and elastin), adipose tissue (fat), and Cooper's ligaments. The ratio of glands to adipose tissues rises from 1:1 in nonlactating women to 2:1 in lactating women.[2]

The breasts sit over the pectoralis major muscle and usually extend from the level of the 2nd rib to the level of the 6th rib anteriorly. The superior lateral quadrant of the breast extends diagonally upwards towards the axillae and is known as the tail of Spence. A thin layer of mammary tissue extends from the clavicle above to the seventh or eighth ribs below and from the midline to the edge of the latissimus dorsi posteriorly. (For further explanation, see anatomical terms of location.)

The arterial blood blood supply to the breasts is derived from the internal thoracic artery (formerly called the internal mammary artery), lateral thoracic artery, thoracoacromial artery, and posterior intercostal arteries. The venous drainage of the breast is mainly to the axillary vein, but there is some drainage to the internal thoracic vein and the intercostal veins. Both sexes have a large concentration of blood vessels and nerves in their nipples. The nipples of both females and males can become erect in response to sexual stimuli,[3] and also to cold.

The breast is innervated by the anterior and lateral cutaneous branches of the fourth through sixth intercostal nerves. The nipple is supplied by the T4 dermatome.


Lymphatic drainage
About 75% of lymph from the breast travels to the ipsilateral axillary lymph nodes. The rest travels to parasternal nodes, to the other breast, or abdominal lymph nodes. The axillary nodes include the pectoral, subscapular, and humeral groups of lymph nodes. These drain to the central axillary lymph nodes, then to the apical axillary lymph nodes. The lymphatic drainage of the breasts is particularly relevant to oncology, since breast cancer is a common cancer and cancer cells can break away from a tumour and spread to other parts of the body through the lymph system by metastasis.


Shape and support

Relatively round breasts which protrude almost horizontally.Breasts vary in both size and shape, and their external appearance is not predictive of their internal anatomy or lactation potential. The shape of a woman?s breasts is in large part dependent on their support, which primarily comes from the Cooper's ligaments, and the underlying chest on which they rest. The breast is attached at its base to the chest wall by the deep fascia over the pectoral muscles. On its upper surface it is given some support by the covering skin where it continues on to the upper chest wall. It is this support which determines the shape of the breasts. In a small fraction of women, the frontal milk sinuses (ampulla) in the breasts are not flush with the surrounding breast tissue, which causes the sinus area to visibly bulge outward.

In discussing the support of breasts, it is helpful to draw a distinction between breasts which rest on the chest below, and those which do not. High, rounded breasts protrude almost horizontally from the chest wall. All breasts are like this in early stages of development, and such a shape is common in younger women and girls. This protruding or ?high? breast is anchored to the chest at its base, and the weight is distributed evenly over the area of the base of the approximately dome- or cone-shaped breasts. [citation needed]

In the ?low? breast, a proportion of the breasts? weight is actually supported by the chest against which the lower breast surface comes to rest, as well as the deep anchorage at the base. The weight is thus distributed over a larger area, which has the effect of reducing the strain. In both males and females, the thoracic cavity slopes progressively outwards from the thoracic inlet (at the top of the breastbone) above to the lowest ribs which mark its lower boundary, allowing it to support the breasts.

The inframammary fold (or line, or crease) is an anatomic structure created by adherence between elements in the skin and underlying connective tissue[4] and represents the inferior extent of breast anatomy. Some teenagers may develop breasts whose skin comes into contact with the chest below the fold at an early age, and some women may never develop such breasts; both situations are perfectly normal. The relationship of the nipple position to the fold is described as ptosis, a term also applied to other body parts and which refers in general to drooping or sagging. Due to breast weight and relaxation of support structures, the nipple-areola complex and breast tissue may eventually hang below the fold, and in some cases the breasts may extend as far as, or even beyond, the navel. The length from the nipple to the sternal notch (central, upper border) in the youthful breast averages 21 cm and is a common anthropometric figure used to assess both breast symmetry and ptosis. Lengthening of both this measurement and the distance between the nipple and the fold are both characteristic of advancing grades of ptosis.

The end of the breast, which includes the nipple, may either be flat (a 180 degree angle) or angled (angles lower than 180 degrees). Breast ends are rarely angled sharper than 60 degrees. Angling of the end of the breast is caused in part by the ligaments that suspend it, such that the breast ends often have a more obtuse angle when a woman is lying on her back. Breasts exist in a range of ratios between length and base diameter, usually ranging from 1/2 to 1.


Development
Main article: Thelarche
The development of a girl's breasts during puberty is triggered by sex hormones, chiefly estrogen. This hormone has been demonstrated to cause the development of woman-like, enlarged breasts in men, a condition called gynecomastia, and is sometimes used deliberately for this effect in male-to-female sex change hormone replacement therapy.

In most cases, the breasts fold down over the chest wall during Tanner stage development, as shown in this diagram.[5] It is typical for a woman?s breasts to be unequal in size particularly while the breasts are developing. Statistically it is slightly more common for the left breast to be the larger.[6] In rare cases, the breasts may be significantly different in size, or one breast may fail to develop entirely.

A large number of medical conditions are known to cause abnormal development of the breasts during puberty. Virginal breast hypertrophy is a condition which involves excessive growth of the breasts, and in some cases the continued growth beyond the usual pubescent age. Breast hypoplasia is a condition where one or both breasts fail to develop.

In Cameroon, some girls are subjected to breast ironing to stunt breast growth in order to make them less sexually attractive in the belief that this makes them less likely to become a victim of rape.


Changes

Breast with visible stretchmarks.As breasts are mostly composed of adipose tissue, their size can change over time. This occurs for a number of reasons, most obviously when a girl grows during puberty and when a woman becomes pregnant. The breast size may also change if she gains (or loses) weight for any other reason. Any rapid increase in size of the breasts can result in the appearance of stretchmarks.

It is typical for a number of other changes to occur during pregnancy: in addition to becoming larger, the breasts generally become firmer, mainly due to hypertrophy of the mammary gland in response to the hormone prolactin. The size of the nipples may increase noticeably and their pigmentation may become darker. These changes may continue during breastfeeding. The breasts generally revert to approximately their previous size after pregnancy, although there may be some increased sagging and stretchmarks.

The size of a woman?s breasts usually fluctuates during the menstrual cycle, particularly with premenstrual water retention. An increase in breast size is a common side effect of use of the combined oral contraceptive pill.

The breasts naturally sag through aging, as the ligaments become elongated.


Function

Breastfeeding
Main article: Breastfeeding

The breasts of a woman who is six months pregnant.[7]The primary function of mammary glands is to nurture young by producing breast milk. The production of milk is called lactation. (While the mammary glands that produce milk are present in the male, they normally remain undeveloped.) The orb-like shape of breasts may help limit heat loss, as a fairly high temperature is required for the production of milk. Alternatively, one theory states that the shape of the human breast evolved in order to prevent infants from suffocating while feeding.[8] Since human infants do not have a protruding jaw like human evolutionary ancestors and other primates, the infant?s nose might be blocked by a flat female chest while feeding.[8] According to this theory, as the human jaw receded, the breasts became larger to compensate.[8]

Milk production unrelated to pregnancy can also occur. This galactorrhea may be an adverse effect of some medicinal drugs (such as some antipsychotic medication), extreme physical stress or endocrine disorders. If it occurs in men it is called male lactation. Newborn babies are often capable of lactation because they receive the hormones prolactin and oxytocin via the mother's bloodstream, filtered through the placenta. This neonatal liquid is known colloquially as witch's milk.


Sexual role
Breasts play an important part in human sexual behavior. They are one of most visible or obvious female secondary sex characteristics,[9] and play an important role in sexual attraction of partners, and pleasure of the individual. On sexual arousal breast size increases, venous patterns across the breasts become more visible, and nipples harden. During sexual intercourse it is common practice to press or massage breasts with hands. Oral stimulation of nipples and breasts is also common. Some women can achieve breast orgasms. In the ancient Indian work the Kama Sutra, marking breasts with nails and biting with teeth are explained as erotic[10].


Other suggested functions
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Please improve this section by adding citations to reliable sources. Unverifiable material may be challenged and removed. (tagged since September 2007)

Zoologists point out that no female mammal other than the human has breasts of comparable size, relative to the rest of the body, when not lactating and that humans are the only primate that has permanently swollen breasts. This suggests that the external form of the breasts is connected to factors other than lactation alone.

One theory is based around the fact that, unlike nearly all other primates, human females do not display clear, physical signs of ovulation. This could have plausibly resulted in human males evolving to respond to more subtle signs of ovulation. During ovulation, the increased estrogen present in the female body results in a slight swelling of the breasts, which then males could have evolved to find attractive. In response, there would be evolutionary pressures that would favor females with more swollen breasts who would, in a manner of speaking, appear to males to be the most likely to be ovulating.

Some zoologists (notably Desmond Morris) believe that the shape of female breasts evolved as a frontal counterpart to that of the buttocks, the reason being that whilst other primates mate in the rear-entry position, humans are more likely to successfully copulate by mating face to face, the so-called missionary position. A secondary sexual characteristic on a woman?s chest would have encouraged this in more primitive incarnations of the human race, and a face on encounter may have helped found a relationship between partners beyond merely a sexual one.[11]


Cultural status

In art, religion, and legend

Edouard Manet, ?Blonde Woman With Bare Breasts?Historically, breasts have been regarded as fertility symbols, because they are the source of life-giving milk. Certain prehistoric female statuettes?so-called Venus figurines?often emphasised the breasts, as in the example of the Venus of Willendorf. In historic times, goddesses such as Ishtar were shown with many breasts, alluding to their role as protectors of childbirth and mothering. The legendary tribe of Amazons bared their breasts, and in some accounts removed one breast to allow better combat and archery.

Some religions afford the breast a special status, either in formal teachings or in symbolism. Islam forbids public exposure of the female breasts.[12] In Christian iconography, some works of art depict women with their breasts in their hands or on a platter, signifying that they died as a martyr by having their breasts severed; one example of this is Saint Agatha of Sicily. In Silappatikaram, Kannagi tears off her left breast and flings it on Madurai, cursing it, causing a devastating fire.


In practice
Breasts are secondary sex characteristics and sexually sensitive. Bare female breasts can elicit heightened sexual desires from men and women. Cultures that associate the breast primarily with sex (as opposed to with breastfeeding) tend to designate bare breasts as indecent, and they are not commonly displayed in public, in contrast to male chests. Other cultures view female toplessness as acceptable, and in some countries women have never been forbidden to bare their chests; in some African cultures, for example, the thigh is highly sexualised and never exposed in public, but the breast is not taboo. Opinion on the exposure of breasts often depends on the place and context, and in some Western societies exposure of breasts on a beach may be acceptable, although in town centres, for example, it is usually considered indecent. In some areas the prohibition against the display of a woman?s breasts only restricts exposure of the nipples.

Women in some areas and cultures are approaching the issue of breast exposure as one of sexual equality, since men (and pre-pubescent children) may bare their chests, but women and teenage girls are forbidden. In the United States, the topfree equality movement seeks to redress this imbalance. This movement won a decision in 1992 in the New York State Court of Appeals??People v. Santorelli?, where the court ruled that the state?s indecent exposure laws do not ban women from being barebreasted. A similar movement succeeded in most parts of Canada in the 1990s. In Australia and much of Europe it is acceptable for women and teenage girls to sunbathe topless on some public beaches and swimming pools, but these are generally the only public areas where exposing breasts is acceptable.

When breastfeeding a baby in public, legal and social rules regarding indecent exposure and dress codes, as well as inhibitions of the woman, tend to be relaxed. Numerous laws around the world have made public breastfeeding legal and disallow companies from prohibiting it in the workplace. Yet the public reaction at the sight of breastfeeding can make the situation uncomfortable for those involved.

See also modesty, nudism and exhibitionism.


Clothing
Since the breasts are flexible, their shape may be affected by clothing, and foundation garments in particular. A brassiere (bra) may be worn to give additional support and to alter the shape of the breasts. There is some debate over whether such support is desirable. A long term clinical study showed that women with large breasts can suffer shoulder pain as a result of bra straps,[13] although a well fitting bra should support most of the breasts? weight with proper sized cups and back band rather than on the shoulders.


Plastic surgery
Plastic surgical procedures of the breast include those for both cosmetic and reconstructive surgery indications. Some women choose these procedures as a result of the high value placed on symmetry of the human form, and because they identify their femininity and sense of self with their breasts.

After mastectomy (the surgical removal of a breast, usually to treat breast cancer) some women undergo breast reconstruction, either with breast implants or autologous tissue transfer, using fat and tissues from the abdomen (TRAM flap) or back (latissiumus muscle flap).

Breast reduction surgery is a common procedure which involves removing excess breast tissue, fat, and skin with repositioning of the nipple-areolar complex (NAC). Cosmetic procedures include breast lifts (mastopexy), breast augmentation with implants, and procedures that combine both elements. Implants containing either silicone gel or saline are available for augmentation and reconstructive surgeries. Surgery can repair inverted nipples by releasing ductal tissues which are tethering. Breast lift with or without reduction can be part of upper body lift after massive weight loss body contouring.

Any surgery of the breast carries with it the potential for interfering with future breastfeeding,[14][15][16] causing alterations in nipple sensation, and difficulty in interpreting mammography (xrays of the breast). A number of studies have demonstrated a similar ability to breastfeed when breast reduction patients are compared to control groups where the surgery was performed using a modern pedicle surgical technique.[17][18][19][20] Plastic surgery organizations have generally discouraged elective cosmetic breast augmentation surgery for teenage girls as the volume of their breast tissue may continue to grow significantly as they mature and because of concerns about understanding long-term risks and benefits of the procedure.[21] Breast surgery in teens for reduction of significantly enlarged breasts or surgery to correct hypolasia and severe asymmetry is considered on a case by case basis by most surgeons.


Disorders
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Infections and inflammations
These may be caused among others by trauma, secretory stasis/milk engorgement, hormonal stimulation, infections or autoimmune reactions. Repeated occurrence unrelated to lactation requires endocrinological examination.

A 1930 Soviet poster. Are you taking care of your breasts? Harden your nipples with daily washing in cold water.Mastitis
bacterial mastitis
mastitis from milk engorgement or secretory stasis
mastitis of mumps
chronic intramammary abscess
chronic subareolar abscess
tuberculosis of the breast
syphilis of the breast
retromammary abscess
actinomycosis of the breast
Mondor?s disease
duct ectasia syndrome
breast engorgement

Benign conditions
Benign conditions include:

Congenital disorders
inverted nipple
supernumerary nipples/supernumerary breasts (polymazia / polymastia) /duplicated nipples
Aberrations of normal development and involution
cyclical nodularity
breast cysts
fibroadenoma - benign tumor
gynecomastia (males)
nipple discharge, galactorrhea
mammary fistula
Fibrocystic disease / Fibrocystic changes
cysts
epithelial hyperplasia
epithelial metaplasia
papillomas
adenosis
Pregnancy-related
galactocoele

Pre-malignant diseases
Carcinoma in situ, a pre-malignant condition which can progress to a malignant cancer

Malignant diseases
Malignant diseases include:

Breast cancer
Paget?s disease of the nipple, also known as Paget?s disease of the breast

See also
Cleavage (breasts)
Breast fetishism
Breast self-examination
Intimate part
Mammary intercourse
Teat
Milk line
Wonderbra
Breast bondage

References
^ Introduction to the Human Body, fifth ed. John Wiley & Sons, Inc.: New York, 2001. 560.
^ a b Anatomy of the lactating human breast redefined with ultrasound imaging, D.T. Ramsay et al., J. Anat. 206:525-34.
^ www.mckinley.uiuc.edu/Handouts/female_f ... ction.html.
^ Boutros S, Kattash M, Wienfeld A, Yuksel E, Baer S, Shenaq S. The intradermal anatomy of the inframammary fold. Plast Reconstr Surg. 1998 Sep; 102(4):1030-3. PMID
^ A.R. Greenbaum, T. Heslop, J. Morris and K.W. Dunn, An investigation of the suitability of bra fit in women referred for reduction mammaplasty, Br J Plast Surg 56 (2003) (3), pp. 230?236
^ C.W. Loughry, et al (1989). "Breast volume measurement of 598 women using biostereometric analysis". Annals of Plastic Surgery 22 (5): 380 ? 385.
^ A Woman's Body: Breasts are Not Just for Filling Sweaters. Available online
^ a b c Bentley, Gillian R. (2001). "The Evolution of the Human Breast". American Journal of Physical Anthropology 32 (3Cool.
^ secondary sex characteristics
^ Sir Richard Burton's English translation of Kama Sutra
^ Morris, Desmond (1967). The Naked Ape: a zoologist's study of the human animal. Canada: Bantam Books, 64?68. N3924.
^ ?They shall cover their chests? or ?they should draw their khimar (veils) over their bosoms?, depending on the translation, Quran (24:31). Available online
^ Ryan, EL, Pectoral girdle myalgia in women: a five-year study in a clinical setting. Clin J Pain. 2000 Dec; 16(4):298-303.
^ Neifert, M; DeMarzo S, Seacat J, Young D, Leff M, Orleans M (1990). "The influence of breast surgery, breast appearance and pregnancy-induced changes on lactation sufficiency as measured by infant weight gain". Birth 17 (1): 31?38. PMID 2288566. Retrieved on 2007-02-11.
^ FAQ on Previous Breast Surgery and Breastfeeding. La Leche League International (2006-08-29). Retrieved on 2007-02-11.
^ West, Diana. Breastfeeding After Breast Surgery. Australian Breastfeeding Association. Retrieved on 2007-02-11.
^ Cruz-Korchin, N; Korchin L (2004-09-15). "Breast-feeding after vertical mammapla

Well... maybe, maybe not.

[RefD]

it's beyond me...

help me, mommy!

[tubemonkey35]

Really though at the end of the day Digital is just trying to mimic anaolg minus some of the "bad" things that come along with it.

[i am monster face]

eally though at the end of the Digital is just trying to mimic anaolg minus some of the "bad" things that come along with it.

Studi-what? StudiYO.

Ian

[JGriffin]

We're still doing this? Really?

[RefD]

[joelmoore]

[RefD]

[i am monster face]

Hugs are simple and fun.

[trodden]

I grew this!!

[MichaelAlan]

That plant looked like something else for a second...


"i grew this"

Ya my buddy went to jail for that...



[/url]

[trodden]

opium is fun!

gardening is Fun!

[hughmanatee]

here is the best way to look at such a debate.

analog is like having boobs right in front of you, that you can play with; given you got some work to do before you can play with them. You'll definately need to devote some significant personal time to routine cleaning and maintenance. It must be treated well, there is a lot of chemistry involved, and unless you fuck it up, it will remain loyal and fruitful for many many years. And the product is pleasing for you and your client(s).


digital is like watching scrambled porn. sure its fun if you dont already know how to play with boobs. But much less work is expected of you; all you got to do is turn the screen on, push a couple buttons, sit there for a bit and BAM! you got product on your hands. it tends to get old and repetitive after a while, and you may even find your self seeking out the supple bottom end that only analog has to offer.