Analog-to-digital conversion (which is variously written as AD conversion, A-D conversion, A/D conversion, and A-to-D conversion) is the process of converting an analog audio signal into a digital format. Analog is the continuously variable signal we encounter in real life. Digital is data represented as binary digits (called bits) that can be read by a computer. This conversion is carried out by a device called an analog-to-digital converter (abbreviated as ADC as well as the various methods indicated for the conversion term).
Obviously, digital-to-analog conversion and converters are what change the data back into analog signals. You will sometime encounter the term AD/DA converter, which refers to both A-to-D or D-to-A converters or to converters that do both, also written variously as AD-DA or ADDA.
The process of converting an analog signal into digital is done by taking a sample, that is, measuring the voltage of the signal, at various intervals. How often the sample is taken is called the sample rate, sampling rate, sample frequency, or sampling frequency. The sample rate for a compact disc is 44.1 kHz or 44,100 times per second. For DVDs, the rate is 48 kHz.
Resolution is the indication of how finely we can measure or display something. For example, print resolution, measured in dots per inch (dpi) indicates how accurately a printer can print. Screen resolution, measured in pixels, indicates how finely a picture can be displayed on a television or computer monitor. For music files, the resolution is indicated by bit depth, which is sometimes called sample depth, bit width, bit resolution, and incorrectly bit rate. (Bit rate is how fast a data stream is transmitted or processed in a given time period, usually expressed in bits per second [bps]).
A higher bit depth represents the amplitude of the sample more accurately and has a greater dynamic range, which in turn provides more headroom during recording. It is very common in the studio to record using a higher bit depth of 24 bits, even though the final product will be converted back to the CD bit depth of 16 bits. The higher resolution provides more flexibility and greater headroom during tracking, making the engineer's job easier.
Two terms that are being used quite frequently and often interchangeably although they are technically different is high-resolution audio and high-definition audio. High-resolution audio (HRA) is an audio file that has a bit depth greater than the normal 16-bit CD specification. High definition audio (HDA) is audio with a bit depth greater than 16 bits and/or a sample rate greater than the normal CD rate of 44.1kHz. While currently there are no standards for HRA, it has been reported that the record industry is working on trying to establish such standards. The other debate is whether the human ear can even has the ability to hear the difference between CD quality and so-called better than CD quality. Various audio publications have taken up sides. I assume that, sooner or later, someone will conduct a double-blind test to end this debate. And there is one other wrinkle. Much of the music available today was recorded on CD-quality equipment. Even if those files are upsampled to higher resolution and sample rates, the quality will not increase. So what's the point?
After nearly 4 years of publishing a Tip of the Month, we have finally run out. So rather than start recycling them, we have decided to start a new series with this issue: Music Trivia. You can find the first installment below. And if you have any tips we missed, let us know and we will pass them on. By the way, all of the tips of the month can be found on our website.
• According to an article in the July/August 2014 issue of Discover magazine, people who cannot sing can recognize the correct note, but they are unable to reproduce it correctly when they try to sing. In other words, they think they are singing well, which is probably obvious to viewers of American Idol.
• The 1969 hit "Sweet Caroline" was about Caroline Kennedy, daughter of President John F. Kennedy, which Neil Diamond finally revealed in 2007 after years of keeping it secret.
Present this coupon when you come in for a recording session and receive $50.00 off the regular rates when you book a session of 8 hours or more. This coupon is good for new clients only, can be used only one time (only one coupon per person or band), and cannot be combined with any other offers. If you pay by phone using a credit card, please use coupon code NEWSLETTER. If you have any friends or relatives looking for a recording studio, please clip this coupon and pass it along to them.