Nyquist Rate

The lowest sampling rate that can be used to record and reproduce a given audio signal, equivalent to twice the highest frequency. If the highest frequency found in an analog signal or sound is 18,000 kHz, theoretically the signal must be sampled at a minimum of 36,000 kHz per second—otherwise, the signal is considered to be undersampled and aliasing will occur. This is essentially the inverse principle of the Nyquist Frequency. (NOTE: the sample rate of 44,100 kHz/second is considered the standard sample rate because it easily covers the upper range of human hearing, which is about 20,000 kHz.)