Bit Depth
sound as numbers. These numbers are stored as binary numbers using only ones and zeros. Binary numbers are similar to decimal numbers we are all familiar with except that the highest number for any digit is 1 compared to 9 for decimal numbers. The following table shows 0-17 in decimal and binary numbers:

 Decimal Binary 0 0 1 1 2 10 3 11 4 100 5 101 6 110 7 111 8 1000 9 1001 10 1010 11 1011 12 1100 13 1101 14 1110 15 1111 16 10000

When you reach the highest number, you have to add a digit. In decimal, this is 9. In binary, it's 1.

Digits in binary are also referred to as bits. From this table you can see that you can represent the number 7 in binary with 3 bits: 111 but that it takes 5 bits to represent the number 16 in binary: 10000.

When storing sound as numbers, the bigger the range of numbers you can use, the lower the distortion (THD: total harmonic distortion) and greater the dynamic range.

CDs store audio data using 16 bit numbers. This means that the highest number is 65535 (1111111111111111 binary). This is generally considered adequate for finished product but is not acceptable when recording the tracks since you'll end up adjusting the volume of tracks and usually compressing them which will sometimes take small values bigger. When this happens the sound gets gritty since you are not adding new data.

Coming soon..

• Graphics depicting bit depth

Wikipedia has more on audio bit depth.