Communication Acoustics: An Introduction to Speech, Audio and Psychoacoustics

3 Signal Processing and Signals

Sound and voice cause vibration or wave propagation in a medium. If we register the value of a vibration of a wave field variable in a spatial position as a function of time, the result is a sound signal. This can be performed using a microphone or a vibration sensor, resulting in an electrical signal that can be processed and stored. Sound signals in electrical form can also be reconverted to sound by using loudspeakers.

Signal processing is the branch of engineering that provides efficient methods and techniques to analyse, synthesize, and transform signals. This chapter presents briefly signal processing fundamentals with regard to sound and voice signals.

3.1 Signals

Signals that use electrical or electronic circuits and work with signal values on a continuous scale are called analogue signals and methods that process them are called analogue signal processing. Such signals are, in most cases, considered to be continuously observable in time and thus are called continuous-time signals. If such a continuous-time signal is sampled properly at specific moments in time, a discrete-time signal is obtained. When these samples are further converted to discrete numbers, the result is called a digital signal. Methods and techniques to cope with such number sequences are called digital signal processing, or DSP for short.

3.1.1 Sounds as Signals

A signal, such as a wave or vibration variable as stated above, is a function of time that can be represented ...