Speech and Audio Signal Processing: Processing and Perception of Speech and Music, Second Edition

CHAPTER 15

PSYCHOACOUSTICS

15.1 INTRODUCTION

Psychoacoustics is the science in which we quantify the human perception of sounds. The ultimate aim is to derive a quantitative model that matches the results of all auditory experiments that we can contrive. This is quite a tall order, since, to a great extent, the human auditory system remains a “black box,” despite many years of physiological research. In this chapter we survey some of the results that have the most obvious relevance to speech and audio applications. Where possible, we correlate psychoacoustical phenomena with physiological measurements.

We can establish some objective variables that will be adjusted in order to assess human perception of sounds. For frequency and intensity, standardized instruments can produce outputs that are linearly proportional to the stimulus. For example, a device that counts the number of zero crossings of a sinusoid over a prescribed time interval can be calibrated to read what we can define as the frequency of the signal. A measure of the spectrum of a sound can also be defined, for instance by a particular form of spectrogram. Duration is another objective property of a sound.

Each of these sound characteristics has a corresponding perceptual variable. The perception of frequency is called pitch, the perception of intensity is called loudness, and the perception of spectrum is called ...