Calculate sampling rate for recordings - how it works

With a few formulas you can calculate the sampling rate for audio recordings. Depending on what your goal is, a different sample rate can mean a minimum file size with maximum benefit.

How to calculate the required sampling rate

The optimal sampling frequency of your audio recording depends on what you value: Each sample rate is a compromise between sound quality, intelligibility, file size and compatibility:

• In general: Since the conversion of sample rates rarely works without loss, you should always carry out all steps in the target sample rate.
• This affects the recording, playback and editing, such as cutting and adding effects.
• That means a sampling rate of 44.1 kHz for audio CDs and typically 48 or 96 kHz for DVD and Blu-Ray.
• Otherwise, the Nyquist-Shannon theorem applies: The sample rate fₓ should be at least twice as high as the critical frequency fᵨ, ie the highest frequency to be recorded, i.e. fₓ> 2 × fᵨ.
• If you want to choose the sample rate so that you do not exceed a certain file size G, use the following formula:
• You can calculate the file size G of a PCM recording, i.e. of uncompressed WAV or AIFF files, as follows: G = D × fₓ × number of audio channels × recording time, where D is the sample depth and the recording time is given in seconds. For MP3 and AAC, you can expect G ≈ bit rate × recording time.
• Unlike the sampling rate, the sample depth is the same. More bits cannot harm the quality, in the worst case they would take up unnecessarily much computing time and storage space or be incompatible with cheap hardware.
• It is even common for digital audio effects to calculate 32 bits internally, even if you end up with only 16 to 24 bits.
• If you need a temporal accuracy of less than 23 µs, you must set the sample rate higher than 44100 Hz.
• DVDs support up to 192 kHz for mono and stereo, and at least 96 kHz for more channels. Blu-Ray support up to six 192 kHz channels or up to eight 96 kHz channels. Make sure that your playback device also masters such high sample rates.
• At Apple, only a few devices have a sample rate of 192 kHz: MacBook Pro (Retina, 13- or 15-inch from 2013), Mac Pro (from the end of 2013), iMac (21.5-inch, mid-2014) and Mac mini (end of 2014 ).
• A sample rate of 32 kHz is the quality of audio tapes that do not record and reproduce the entire audible spectrum, but reach up to about 14.5 kHz.
• In order to achieve good speech intelligibility with small file sizes for voice recordings, recording at 22050 Hz sample rate with subsequent conversion to MP3 or AAC with 56 to 64 bits per channel is suitable.
• With a sample rate of 8 kHz you do not quite achieve the quality of telephone transmissions or some mini dictation machines.
• By the way: To record the pure pitch of melodies, regardless of the sound quality, around 1400 Hz is more sufficient for men, 1800 Hz for women.