ADC(Analog to Digital Conversion)

The conversion of analog signals in nature to digital signals is one of the most important procedures in audio signal processing.

 

Since sound waveforms can be understood in terms of two-dimensional graphs, there are two keywords when implementing ADC.

 

Sampling

Sampling is a reduction of continuous-time signal to a discrete-time signal.

https://en.wikipedia.org/wiki/Sampling_(signal_processing)

It extracts values(especially air pressure) from original signal with a constant rate, which is called a sample rate.

Note that 

sr = 1/T

One of the most important theories when performing sampling will be nyquist-shannon sampling theory.

According to this theory, nyquist frequency is the upper bound of the soundwave frequency that can be restored from digital signals. 

https://en.wikipedia.org/wiki/Nyquist_frequency

To understand this concept, one must have pre-understanding of fourier transform and aliasing.

 

Quantization

Quantization is a reduction of the "value" axis of analog soundwaves. 

https://en.wikipedia.org/wiki/Quantization_(signal_processing)#/media/File:2-bit_resolution_analog_comparison.png

 

Thus, we can expect that if we have information of sampling rate and quantization resolution, we will be able to compute the maximum memory used to save a specific audio signal.