Psychoacoustics

The study of the relationship between physical SOUNDs and the brain's interpretation of them. Until recently, psychoacoustics has devoted more attention to the behaviour of the peripheral auditory system than to the details of cognitive processing.

The discipline is a branch of psychophysics in that it is interested in the relation between sensory input stimuli and the behavioural or psychological RESPONSE that they provoke. Because of individual variations in observed responses, statistical results are most often achieved.

Some of the traditional psychoacoustic concerns involve the perception of PITCH, LOUDNESS, VOLUME and TIMBRE. Contemporary work involves higher level concepts such as auditory percepts, streaming, and auditory scene analysis.

A great deal has been learned in this century about the behaviour of the human auditory system in the way it processes incoming sound waves and extracts usable information, The basic subjective concepts involved are:

a) "response" characteristics, that is, how the magnitude of the sensation caused by the stimulus relates to the physical magnitude of the stimulus;

b) the "threshold" of sensation;

c) the "just noticeable difference" in a certain parameter of the stimulus;

d) the "resolution" or "resolving power" of the system to separate simultaneous stimuli, or the way simultaneous stimuli cause a composite sensation;

e) how stimulus sensation changes over time.


 The study of the relationship between physical vibrations and the brain's interpretation of them is the Psychoacoustics Psychoacoustics. The mental processes which extract sound features for purposes of memory storage, intelligibility and problem solving are studied by the  SONOLOGY. Psychoacoustics study the processing of incoming sound waves by the auditory system to extract usable information for the brain, the process most commonly called "hearing".

 

 

 

 

Physiology & Psychoacoustics


Psychoacoustics

Psychoacoustics is the science that deals with the perception of sound. Sound arrives at our ears as pressure waves which are processed and converted into the perception of sound. Whereas physical sound can be measured the same by different individuals, the perception of sound will vary from one individual to another.


 

Hearing

The human auditory system is complex in structure and remarkable in function. Not only does it respond to a wide range of stimuli, but it precisely identifies the pitch and timbre (quality) of a sound and even the direction of the source. The frequency range of hearing extends from 20 to 20,000 Hz for some, substantially less for others.

In this chapter you will learn about how the auditory system perceives sounds, how it works with the central nervous system, and which parameters of hearing are subjective (different for every person).

Hearing function


Dynamic range


Frequency response


Sensitivity


Prebycusis


SelectivityStructure of the ear


Outer ear


Middle ear


Inner ear Signal processing


Tuning curves


Critical bands (critical bandwidth)


Binaural hearing


Localization, Precedence effect, Hass effect Psychoacoustics (Fechner's law)


Logarithms


Loudness

A violinist playing a song is joined by another violinist who together play the piece in perfect sync. If both play their violins at the same loudness will their combined loudness be double that of just one violin playing?

In this chapter you will learn how sound is measured, and how frequency, complex tones, and masking have an effect on the perception of loudness.

Measuring Acoustic energy


Sound pressure level


Frequency response


Sound power level


Sound intensity level


Inverse square law


Multiple sources


Perception of acoustic energy


Loudness level (phons)


Loudness of pure tones (sones)


Loudness of complex tones


Musical dynamics


Forward masking

Backward masking

 

Central masking

 

Partial masking

 

Noise

 

White noise

 

Pink noise


Pitch and Timbre

Pitch is a perception of frequency. However there is no direct relationship between pitch and frequency. Ask two different individuals to hum a particular note like "middle C" and they probably will both hum a different note. It may or may not be the frequency of what is known as "middle C"

Timbre is defined as the "tone quality of sound." It is the ability to judge two sounds dissimilar, even though they are presented to you having the same pitch, loudness, and duration. So if two trumpet players each play the same note, at the same pitch for the same amount of time, and at the same loudness, and you can perceive that there are two different sounds, then you have perceived timbre.

Pitch Scales


Octave


Semitones


Mels


Barks


Pitch Discrimination


Just noticeable difference


Frequency resolution


Difference limens


Pitch of pure tones


Steven's Rule


Acoustic uncertainty principle


Pitch of complex tones


Virtual pitch


Pitch theories


Place theory


Periodicity theory


Absolute pitch


Pitch standard (A440)


Perception of timbre


Timbre


Tone quality subjective


Fourier analysis of complex tones


Effects of envelope and duration on timbre


Tristimulus diagrams


Vibrato


Frequency vibrato


Amplitude vibrato


Blend of complex tones


Analytical listening


Synthetic listening


Harmony

Are you able to listen to the radio, watch the TV and carry on a conversation at the same time?

In this chapter we will look at what happens when two or more sounds reach the ear at the same time.

You will learn about beats, combination tones, and superposition.

Beats


Binaural beats


Second-order beats


Non-linear effects


Combination tones


Modulation


Aural harmonics


Summation tones


Musical effects


Musical staff


Musical intervals consonance & dissonance


Pure tones


Complex tones


Chords


Central nervous system


Autocorrelation


Cross- correlation


Cerebral dominance


Scales

The word "scale" is derived from a Latin word (scala) meaning "ladder" or "staircase." A musical scale is a succession of notes arranged in ascending or descending order. Most musical composition is based on scales.

Western music divides the octave into 12 steps called semitones. All the semitones in an octave constitute a chromatic scale or 12-tone scale. However most music makes use of a scale of seven selected notes, designated as either a major scale or a minor scale and carrying the note name of the lowest note.

For example, the C-major scale is played on the piano by beginning with any C and playing white keys until another C is reached.

Musical scales


Pentatonic


Chromatic


Diatonic


Semitones


Scales and temperaments


Just intonation


Pythagorean scale


Meantone temperament


Equal temperament


Electronic tuners


Ratios


Cents