Sound Levels, Spectral Analysis and Notions on Human Sound Perception

This chapter introduces elementary signal processing concepts used in acoustics and their application to the characterization of human sound perception. It discusses the power spectral density, along with the related notion of correlation functions, which is the basic tool for analysis of the frequency distribution of sound signals, especially in the frequency range corresponding to human perception. Some concepts related to sound perception by the human ear are then introduced. The sensitivity of the ear varies with the frequency of the sound, but also with its level. This effect is accounted for by defining loudness and their relationship to subjective loudness (sone scale) as perceived by humans. While most of the concepts introduced in the chapter apply to signals whose average power does not vary with time (stationary signals), the case of non-stationary signals whose average characteristics evolve with time, in particular transient signals, is briefly discussed at the end of the chapter.