What is the Nyquist frequency?
The Nyquist frequency is a term from information theory and signal processing. It describes the maximum frequency that an analogue signal can have in order to be correctly converted into a digital signal.
In order to convert an analog signal into a digital signal, it is first measured at regular time intervals (the so-called sampling interval) and the measured values are saved in a special format. The number of times the analog signal is sampled is called the sampling frequency. If the sampling frequency is high enough, the analog signal can be reproduced correctly when later converted back to analog form.
The Nyquist frequency is half the sampling frequency and indicates the maximum frequency that an analog signal can have before it can still be correctly converted into a digital signal. This relationship is called the Nyquist sampling theorem.
Example: If an analog signal with a Sampling frequency of 48 kHz sampled, the Nyquist frequency is 24 kHz. This means that the analogue signal must have a maximum frequency of 24 kHz in order to be correctly converted into a digital signal. Higher frequencies would be lost in the conversion and could not be reproduced.