Speech signal processing (III): speech signal analysis [continuous "analog signal" -- Sampling, quantization, coding -- > discrete "digital signal"]

One 、 Time domain and frequency domain

For a pure tone , A pure tone signal has only one frequency , Its frequency can be obtained by calculation 、 Phase and amplitude . Pure tones are rare in nature , Most sounds are compound , That is, a sound containing several frequency components .

When we want to process sound , From their time domain waveform to analyze , Find it difficult to . Each pure tone corresponds to a fixed frequency , Analyze the signal from the angle of frequency , The original complex signals become clear .

Audio is our most common understanding of music , A vibration that changes over time , It's real , Every detail is vivid , We call it Time domain .

The notes of the staff are the materialization of audio , So that the changing audio can be fixed into the concrete symbols we know . We call it frequency domain .

Domain It is the name of analyzing different angles of signals . The time domain is always changing , Is a description of the real world . The frequency domain is artificially defined by us , An expression of a mathematical formula , In music, it is expressed by musical symbols . Time domain is an objective domain , The frequency domain is mathematically constructed .

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