HEARING: PHYSIOLOGY AND
PSYCHOACOUSTICS
LITERATURE
• Goldstein, E. and Cacciamani, L. (2022). Hearing (Ch.11).
• Wolfe, J.M. et al. (2019/2022). Hearing: physiology and psychoacoustics (Ch.9).
• Caruso, C. (2016). Can You Hear Me Now? Detecting Hidden Hearing Loss in Young People.
Scientific American.
LEARNING GOALS
1. sound graphs, how to read them etc.?
2. sound perception and anatomical basics
3. whats the role of the Fourier analysis
4. causes and types of hearing loss
5. hidden hearing loss
6. auditory tuning curbs
WHAT IS SOUND?
• The vibrations of the sound source cause molecules in the
object’s surrounding medium to vibrate as well
o This vibration causes pressure changes in the
medium
o These pressure changes are waves
o The pattern of displacement will move outward from
the source until something gets in the way
o The initial amount of pressure change is dispersed
over a larger and larger area as the wave moves
away, so the wave becomes less prominent as it
moves farther from it source
• Sound waves travel at different speeds through different
media à faster through denser substances
o Speed of sound through air = 340 m/s
o Speed of sound through water = 1500 m/s
FOURIER ANALYSIS
• Fourier analysis identifies contributions at different frequencies, allowing us to reconstruct the
individual signals that went into it
, • Takes a time-based pattern, measures every possible cycle and returns the overall ‘cycle recipe’
(amplitude, offset and rotation speed for every cycle that was found)
BASIC QUALITIES OF SOUND WAVES: FREQUENCY AND AMPLITUDE
o Sound waves we hear are fluctuations in air pressure across time
Amplitude = magnitude of displacement (increase/decrease) of a pressure wave. Perceived as loudness
o Pressure fluctuations may be very close together or spread apart over longer periods
o Associated with loudness; the more intense a sound wave is, the louder it will sound
o measured on a logarithmic scale using units called Decibels (dB)
§ Define the difference between two sounds in terms of the ratio between sound
pressures
§ Each 10:1 sound pressure ratio is equal to 20 dB, so 100:1 ratio = 40 dB
P = pressure (intensity) of the sound
Po = reference pressure, 0.0002 dyne/cm2, levels defined in terms of dB SPL (sound pressure level)
If the pressure of the sound you’re measuring (p) = 0.0002 dyne/cm2, then dB=20log(1)
o Because log(1) = 0, a sound pressure that low would be 0 dB SPL
o NOT silence ; sounds with amplitudes even smaller than Po have negative decibel levels
Relatively small decibel changes can correspond to large physical changes
Frequency = the number
of times per second that a
pattern of pressure
change repeats.
Perceived as pitch
o à the rate of
fluctuation
o Associated with pitch; low frequency sounds correspond to low pitches, and high frequency
sounds correspond to high pitches
o Unit of measure = Hertz
§ 1 cycle / second = 1 Hz
, o Humans can hear frequencies that range from 20 to 20,000 Hz across a very wide range of
intensities, or sound pressure levels
o Pressure in a 500 Hz wave goes from highest point to lowest point and back 500 times /
second
SINE WAVES AND COMPLEX SOUNDS
Sine wave / pure tone = a pressure change pattern that can be described with a sine wave
o Any sound can be described as a combination of sine waves by Fourier analysis
o Pure tones are rare in the environment
Complex tone = composed of other tones
o Best described with a frequency spectrum, which displays how much amplitude is present at
multiple frequencies
Spectrum = a representation of the relative energy (intensity) present at each frequency
• The shape of the spectrum (spectral shape) is one of the most important qualities
that distinguish different sounds
o The properties of sound sources determine the spectral shapes of
sounds, and these shapes help us identify sound sources
o Spectra from 3 different
instruments
o Each instrument is
producing a note with the
same fundamental
frequency & harmonics
o BUT the shapes of the
spectra (patterns of
amplitudes for each
harmonic) vary
Harmonic spectrum = the spectrum of a complex sound in which energy is an integer multiples of the
fundamental frequency
o Caused by a simple vibrating source
o Each frequency component in such a sound = harmonic
PSYCHOACOUSTICS
LITERATURE
• Goldstein, E. and Cacciamani, L. (2022). Hearing (Ch.11).
• Wolfe, J.M. et al. (2019/2022). Hearing: physiology and psychoacoustics (Ch.9).
• Caruso, C. (2016). Can You Hear Me Now? Detecting Hidden Hearing Loss in Young People.
Scientific American.
LEARNING GOALS
1. sound graphs, how to read them etc.?
2. sound perception and anatomical basics
3. whats the role of the Fourier analysis
4. causes and types of hearing loss
5. hidden hearing loss
6. auditory tuning curbs
WHAT IS SOUND?
• The vibrations of the sound source cause molecules in the
object’s surrounding medium to vibrate as well
o This vibration causes pressure changes in the
medium
o These pressure changes are waves
o The pattern of displacement will move outward from
the source until something gets in the way
o The initial amount of pressure change is dispersed
over a larger and larger area as the wave moves
away, so the wave becomes less prominent as it
moves farther from it source
• Sound waves travel at different speeds through different
media à faster through denser substances
o Speed of sound through air = 340 m/s
o Speed of sound through water = 1500 m/s
FOURIER ANALYSIS
• Fourier analysis identifies contributions at different frequencies, allowing us to reconstruct the
individual signals that went into it
, • Takes a time-based pattern, measures every possible cycle and returns the overall ‘cycle recipe’
(amplitude, offset and rotation speed for every cycle that was found)
BASIC QUALITIES OF SOUND WAVES: FREQUENCY AND AMPLITUDE
o Sound waves we hear are fluctuations in air pressure across time
Amplitude = magnitude of displacement (increase/decrease) of a pressure wave. Perceived as loudness
o Pressure fluctuations may be very close together or spread apart over longer periods
o Associated with loudness; the more intense a sound wave is, the louder it will sound
o measured on a logarithmic scale using units called Decibels (dB)
§ Define the difference between two sounds in terms of the ratio between sound
pressures
§ Each 10:1 sound pressure ratio is equal to 20 dB, so 100:1 ratio = 40 dB
P = pressure (intensity) of the sound
Po = reference pressure, 0.0002 dyne/cm2, levels defined in terms of dB SPL (sound pressure level)
If the pressure of the sound you’re measuring (p) = 0.0002 dyne/cm2, then dB=20log(1)
o Because log(1) = 0, a sound pressure that low would be 0 dB SPL
o NOT silence ; sounds with amplitudes even smaller than Po have negative decibel levels
Relatively small decibel changes can correspond to large physical changes
Frequency = the number
of times per second that a
pattern of pressure
change repeats.
Perceived as pitch
o à the rate of
fluctuation
o Associated with pitch; low frequency sounds correspond to low pitches, and high frequency
sounds correspond to high pitches
o Unit of measure = Hertz
§ 1 cycle / second = 1 Hz
, o Humans can hear frequencies that range from 20 to 20,000 Hz across a very wide range of
intensities, or sound pressure levels
o Pressure in a 500 Hz wave goes from highest point to lowest point and back 500 times /
second
SINE WAVES AND COMPLEX SOUNDS
Sine wave / pure tone = a pressure change pattern that can be described with a sine wave
o Any sound can be described as a combination of sine waves by Fourier analysis
o Pure tones are rare in the environment
Complex tone = composed of other tones
o Best described with a frequency spectrum, which displays how much amplitude is present at
multiple frequencies
Spectrum = a representation of the relative energy (intensity) present at each frequency
• The shape of the spectrum (spectral shape) is one of the most important qualities
that distinguish different sounds
o The properties of sound sources determine the spectral shapes of
sounds, and these shapes help us identify sound sources
o Spectra from 3 different
instruments
o Each instrument is
producing a note with the
same fundamental
frequency & harmonics
o BUT the shapes of the
spectra (patterns of
amplitudes for each
harmonic) vary
Harmonic spectrum = the spectrum of a complex sound in which energy is an integer multiples of the
fundamental frequency
o Caused by a simple vibrating source
o Each frequency component in such a sound = harmonic
