Answer to Question #90167 in Physics for Shivam Nishad

Question

What is minimum sampling frequency to sample a base band audio signal for communication ?

Answer 1

Answer:

According to Nyquist-Shannon Sampling Theorem [1]:

In order for a faithful reproduction and reconstruction of an analog signal that is confined to a maximum frequency F_m , the signal should be sampled at a Sampling frequency (F_s) that is greater than or equal to twice the maximum frequency of the signal. [3]

$$F_S \geqslant 2 * F_M$$

So, basically, the sampling rate for an analog signal must be at least two times the bandwidth of the signal.

For example, an audio signal with a bandwidth of 20 kHz must be sampled at least at 40 kHz to avoid aliasing. Thus, in audio CD's, the sampling rate is 44.1 kHz to cover the range of human hearing ( up to 22 kHz) [2].

In telephony, 8 kHz sampling is used, since the usable human voice frequency band ranges from approximately 300 Hz to 3400 Hz [4]. 

So, 8 kHz sampling considered to be minimal sampling frequency for effective voice communication.

References:

1. https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem
2. https://en.wikipedia.org/wiki/Sampling_(signal_processing)
3. https://www.gaussianwaves.com/2011/07/sampling-theorem-baseband-sampling
4. https://en.wikipedia.org/wiki/Voice_frequency