For example, to reproduce sound in the human frequency range of 20 Hz to 20 kHz, the sampling frequency must be higher than 40 kHz. In sounds, the highest frequency is related to higher harmonics produced by various musical instruments. With images, the highest frequency is related to small structures or objects like, for example, grass or sand. The Nyquist-Shannon sampling theorem states that to restore a signal, a sufficient sample rate must be greater than twice the highest frequency of the signal being sampled. The sampling interval or sampling period T s is the reciprocal of the sampling frequency: It is measured in the units of frequency - hertz. The sampling frequency, or sampling rate f s is the number of samples obtain in one second. A sample is a value of an analog signal at a point of time. Sampling is the technique used for recording analog information like audio signals or images by recording their snapshots at periodic intervals.
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