Bit depth describes the number of bits of information recorded for each sample. This directly corresponds to the resolution of each sample.a “bit’ is an abbreviation for a single binary digit, represented by a 0 or 1. A word in audio is a binary number with more than one digit. A 16-bit binary number for example could be 0111011010110010. The number of bits per word is simply how many digits there are in the corresponding number. Common bit depths are 8, 16 and 24 so the higher the quality is the higher the number. The bit depth in recording refers to how many steps the amplitude can be broken down into to be represented digitally.
16 Bit = 65,536 Steps
24 Bit = 16,777,216 Steps
You can clearly see that 24 Bit would be considered higher quality as it is able to plot smoother more accurate lines of amplitude.
The Bit Rate is how many of these bits are being transmitted or received per second. This is used for streaming purposes on videos as well. For playback, using the example of a standard CD with a data rate of 48kHz/24, meaning the sample rate was 48,000 times per second with bit depth of 24. The amount of audio data per second is worked out like this: 48000 x 24 x 2 (for stereo recordings) = 2,304,000 bit/s or 2.3 Mbit/s.
The size of an audio file size can be calculated with a similar equation.The equation below is with the example of recording at 48khz at 24 bit depth, that plays out in stereo (so 2 channels means x2, recording 5 you would mean you x5) for 60 minutes which is 3,600 seconds and divide by 8, you then get this:48000 x 24 x 2 x 3600 / 8 = 1036,800,000 Bytes or 1.036GB.
So bit depth is your resolution for the information for each sample but many would argue there is no massive difference for recording dialogue between 16bit or 24bit but if you have the space why not.See also: Sample Rate Explained.
London Sound Recordist
I am a London Sound Recordist and Sound Editor for many types of projects around the film genres. This covers creative content right through to feature films. I am passionate about sharing my journey and knowledge to help the rest of the community. If you need anything from me, feel free to get in touch with me at London Sound Recordist.