Welcome to this video on Nyquist theory.

Nyquist theory helps determine the minimum acceptable sample rate to ensure good analogue to digital audio conversion for the range of frequency that humans can hear.

During his research into digital data transmission systems in the first half of the 20th century, Harry Nyquist produced a theorem to determine sufficient sample rates for differing audio frequencies.

In simple terms, his theory states that ..

“The sample rate should be a little over twice the highest audio frequency to be recorded if poor sound quality is to be avoided".

Caption - Choosing a sample rate for the audio spectrum

Because humans can hear audio frequencies as high as 20kHz, or 20,000 cycles per second, a minimum sample rate of 44.1kHz, or 44,100 measurements of amplitude per second, is required to accurately represent sound digitally.

As we know, the human audio spectrum stretches from 20Hz to 20,000Hz, or 20kHz. Therefore the highest audible frequency is 20,000Hz. If we double this we get 40,000. Add "a little bit more" and we arrive at a sample rate of 44,100 samples per second, which can be expressed as a sampling frequency of 44.1kHz

Caption - Is a sample rate of 44.1kHz still adequate today?

Today, modern digital electronics makes greater sample rates practical and there has therefore been much discussion about whether 44.1kHz is adequate. In our video on Aliasing we will learn how a sample rate of 44.1kHz does not look ideal. However, although some claim that higher sample rates, such as 96kHz produce a much better sound, others can’t hear any difference at all.

The truth is that unlike hi-definition video where improvements over standard definition are noticeable to the majority of viewers, most listeners will not hear the difference between the CD sample rate of 44.1kHz and higher sample rates.

Studio owners are advised to carry out their own listening tests and decide for themselves. Unless you believe that recording at higher sample rates is sensible to make your recordings future proof, or higher sample rates are demanded by your customers or the requirements of a specific delivery platform such as high definition film work, you can safely record at 44.kHz or 48kHz.

Our video on Aliasing will help you understand how the minimum recommended sample rate of 44.1kHz was arrived at.

Caption - Thanks for watching

The script for this video, with accompanying images, can be found at projectstudiohandbook.com 

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