In the last post we discussed about various audio formats. In this post we look at the best recording format for your audio. For that we need to understand 2 terms, Sampling and bit rate. Digital audio has two primary qualities that compose the way the audio is described. – sampling rate and bit rate.
When you are recording audio digitally, the device (say, your computer) receives the audio signal, by breaking it up into “snapshots” or samples. In recording technology, the number of samples received per second is called the sampling rate. The concept is comparable to a digital movie camera that records a number of image frames per second and plays it back as a continuous moving image. Similarly, you listen to uninterrupted audio playback. Sampling rate is measured in hertz and represents the sound frequency range. Higher the sampling rate greater is the audio quality and ensures greater precision in your high notes and low notes. Standard CD quality incorporates a sampling rate of 44, 100Hz or 44.1 KHz. Sampling rates start from 8000hz(very very low quality) to 196,000(very very high quality, with extreme huge files).
In digital multimedia, bit rate often refers to the number of bits used per unit of playback time to represent a continuous medium such as audio. Let us understand what the bit rate actually represents.While sampling rate is number of samples recorded per second, bit rate refers to the characteristics of each individual sample recorded. Going back to the digital camera example, bit rate is the equivalent of pixels in digital images. Higher the pixels, better is the image quality. Similarly, higher the bit rate (also called bit depth), better is the audio quality. For instance an 8 bit audio will sound grainy and harsh, while a 16 bit audio sounds much better. Standard CD format has 44.1k sampling rate combined with 16 bit rate.
Naturally a 24 bit audio will offer the highest quality, but such files occupy more space and require greater computing power to process and may not be really necessary for the purpose of your audio. For FM transmission or internet streaming 16 bit rates are perfect. Professional audio studios opt for 24 or 32 bit rates, because the higher accuracy it offers is useful in the recording, mixing and mastering process.
Bit Rate in MP3
The MP3 format is lossy audio format that compresses audio files to reduce size by eliminating redundant data. You can choose how much information an MP3 file will retain or lose during the encoding and compression process by tweaking the bit rate. Lower bit rate means that the encoder will discard more information during the compression process, which may affect the audio quality on playback. Bit rates for MP3 encoders range from 16 kilobytes per second (kbps) to 320 kbps. A bit rate of 320 kbps gives CD quality audio and is similar to what you’d hear on the radio. A higher MP3 bit rate provides better audio quality but produces larger files.
Charts comparing various formats and the quality vs size.
|Wave/Aiff||8,000hz-16,000hz||8||Very Low||Very samll|
|48,000Hz and Above||16 bit -32 bit||pristine||Extremely big|
|MP3||8,000hz-16,000hz||16-96 kbps||Very Low||Very small|
|32,000-44,100 hz||96-196 kbps||decent||small|
|44,100 Hz||256-320 kbps||excellent||medium|
So for recording audio always record in wav/aiff at 44,100 Hz and 16 bit. That will give you the perfect quality. If you need to encode/record in mp3, at least 196kbps is minimum for a decent quality.
By Rajiv Agarwal