![]() There is always a gap between any two sampling moments, during which a very brief peak in the sound wave can pass unnoticed. A second practical consequence is the relation between the sampling rate and the temporal resolution of the recording. ![]() In order to take advantage of the recording quality you set, the frequency range of your microphone will have to be better than the Nyquist frequency.The upper frequency limit of microphones depends on their design and intended purpose, from telephone microphones at 3.5 kHz to hi-fi microphones at 20kHz or more. For comparison, the upper limit of telephone transmission is around 3.5kHz, of the loudspeaker of a miniature radio about 3-10kHz depending on size and quality, and FM radio transmission anything up to about 15kHz.Hi-fi recording captures all spectral activity up to 20kHz, requiring a sampling rate of at least 40kHz. To capture all the spectral activity of speech, a Nyquist frequency of around 10kHz is necessary, obtained by setting a sampling rate of 20kHz. That’s not very good for speech since it misses the typical spectral activity of dental consonants that is mostly higher than 5kHz. ![]() To prevent this happening, anti-aliasing filters (also part of the computer sound system) remove this false activity, so that the Nyquist frequency effectively becomes the upper limit of the recording. For example, if the sampling rate is set at 10kHz (10,000 samples a second) then the Nyquist frequency is 5kHz (5,000 cycles per second). Any spectral activity in the digital recording above the Nyquist frequency is useless, since it is distorted and contaminated by spurious false tones ( aliasing). This highest useful sound frequency is known as the Nyquist frequency.
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