Chapter 11: Hearing Flashcards
functions of hearing
- Hearing serves an important signalling function
- It adds richness to our lives through music
- It facilitates communication through speech
sound
describes both a physical stimulus and a perceptual response
physical definition of sound
sound is pressure changes in the air or other medium
the physical definition of sound is a type of ___
sensation
Perceptual definition
sound is the experience we have when we hear
the perceptual definition of sound is a type of ___
perception
sound wave
the pattern of air pressure changes
speed of sound through air
340 m/s
speed of sound through water
1500 m/s
compression/condensation
an increase in the pressure of air molecules
rarefaction
a decrease in the pressure of air molecules
location of air molecules during pressure changes
Although air pressure changes move outward from the source, the air molecules at each location move back and forth and they stay in about the same place
pure tone
when changes in air pressure occur in a pattern described by a sine wave
frequency
the number of cycles per second that the pressure changes repeat
how is frequency measured
hertz
what does hertz represent
the number of cycles per second; 1 Hz represents 1 cycle/second
what is the range of frequencies that humans can detect?
20-20,000 Hz
what perceptual dimension is frequency associated with?
pitch
amplitude
the size of the pressure change
how is amplitude measured?
Decibels (dB)
decibels
a perceptual unit that converts a large range of sound pressures into a more manageable scale
what perceptual dimension is amplitude associated with?
loudness
how are decibels calculated?
dB= 20 x log 10 (p/po)
what does p represent in the decibel equation
the pressure of the sound wave we are considering
what does po represent in the decibel equation?
the reference pressure, usually set at 20 micro pascals (the pressure near the hearing threshold for a 1,000 Hz tone)
Sound pressure level (SPL)
indicates that decibels were determined using the standard pressure of 20 micro pascals
sound level
the sound pressure of a sound stimulus in decibels
are most sounds in the environment sine waves?
no, most sounds in the environment are made up of complex tones, which have more complex patterns than a sine-wave
are complex tones periodic waveforms?
yes
complex tones
made up of pure tone sine-wave components that are added together
periodic waveform
a pattern of repeating pressure changes
fundamental frequency
the first harmonic of a complex tone; usually the lowest frequency in the frequency spectrum of a complex tone.
harmonics
pure-tone components of a complex tone that have frequencies that are multiples of the fundamental frequency
first harmonic
usually the lowest frequency in the frequency spectrum of a complex tone.
fundamental
a pure tone with a frequency equal to the fundamental frequency of a complex tone
higher harmonics
pure tones with frequencies that are whole number multiples of the fundamental frequency
frequency spectra
a plot that indicates the amplitude of the various harmonics that make up a complex tone.
repetition rate
the spacing between harmonics
what happens to the repetition rate if a harmonic is removed?
The repetition rate remains the same even if the fundamental or higher harmonics are removed because the spacing between harmonics remains intact
loudness
a perceptual quality most related to the level or amplitude of an auditory stimulus
audibility curve
a curve that indicates the sound pressure level (SPL) at the threshold for frequencies across the audible spectrum
auditory response area
shows the range of response for human audition. falls between the audibility curve and the threshold for feeling
equal loudness curve
a curve that indicates the sound pressure levels that result in a perception of the same loudness at frequencies across the audible spectrum
pitch
the property of auditory sensation in terms of which sounds may be ordered on a musical scale extending from high to low
what is pitch associated with?
the repetition rate of the sound waveform of the fundamental frequency
tone height
the increasing pitch that accompanies increases in a tone’s fundamental frequency
tone chroma
the perceptual similarity of notes separated by one or more octaves
octave
tones that have frequencies that are binary multiples of each other
effect of the missing fundamental
the fact that pitch remains the same even when the fundamental or other harmonics are removed
timbre
the quality that distinguishes two tones that sound different even though they have the same loudness, pitch and duration. Differences in timbre are illustrated by the sounds made by different musical instruments,
how are different timbres created?
- Differences in the harmonics of different instruments
- The time course of a tone’s attack and decay
attack
the buildup of sound at the beginning of the tone
decay
the decrease in sound at the end of the tone
periodic sounds
a sound stimulus in which the pattern of pressure changes repeats
aperiodic sounds
a sound stimulus in which the pattern of pressure changes and does not repeat
how does the auditory system transduce pressure changes into electrical signals?
- The auditory system delivers the sound stimulus to the receptors
- It transduces this stimulus from pressure changes into electrical signals
- It processes the electrical signals so they can indicate the qualities of the sound source
outer ear
composed of the pinna and the auditory canal
pinnae
the part of the ear that is visible on the outside of the head. it helps with sound location
auditory canal
tube-like 3 cm long structure that protects the delicate structures of the middle ear
Tympanic membrane/eardrum
A membrane at the end of the auditory canal that vibrates in response to vibrations of the air and transmits these vibrations to the ossicles in the middle ear
resonance
A mechanism that enhances the intensity of certain frequencies because of the reflection of sound waves in a closed tube
what frequencies does resonance in the auditory canal enhance?
1,000-5,000 Hz
resonant frequency
The frequency that is most strongly enhanced by resonance
how is the resonant frequency of a closed tube determined?
by the length of the tube
middle ear
the small air-filled space between the auditory canal and the cochlea that contains the ossicles
ossicles
three small bones in the middle ear that transmit vibrations from the outer ear to the inner ear
malleus
the first of the ossicles in the middle ear. Receives vibrations from the tympanic membrane and transmits them to the incus.
incus
the second of the three ossicles of the middle ear. It transmits vibrations from the malleus to the stapes
stapes
The last of the three ossicles in the middle ear. It receives vibrations from the incus and transmits these vibrations to the oval window of the inner ear
oval window
a small, membrane-covered hole in the cochlea that receives vibrations from the stapes