Question

please make a research report on this

its a digital communication subject question.

Sampling frequency of Audio and Speech and required amount of bits. (What and why?)

Answer 1

Explanation: The sampling of analog signal is based on sampling theorem. The sampling theorem states that if fm is the maximum frequency component in the signal can be represented by its sampled version provided the number samples taken per second is greater than or equal to twice the maximum frequency component. The number of samples/second is more commonly termed as sampling frequency fs. According to sampling theorem , fs should be greater than or equal to 2 fm .

The speech signal has frequency components in the audio frequency range (20 Hz to 20 kHz) of the electromagnetism spectrum. This is the reason for perceiving the information present in the speech signal by human ears. The fundamental question is upto what range of audio frequency, the speech signal has frequency components. We can analyze this experimentally by considering the whole audio range. The standard sampling frequency to sample the entire audio range is 44.2 kHz.

After the sampling frequency , the next important parameter in the digitization process of speech is bit resolution.The number of bits used for storing each sample of speech is termed as bit resolution.

All speech signal processing applications invariably use 16 bits/sample as bit resolution. The number of quantization levels will therefore 2^16 =65536 and are found to be optimal for preserving information present in the analog version of the speech signal. The next lower bit length possible with binarypower is 8 bits.The effect of bit resolution can be analyzed experimentally . For this experiment the optimal sampling frequency of 16 kHz can be used as proposed earlier.