Exam 3 Flashcards
psychoacoustics
the study of the perception of sound:
- how we listen
- our physiological responses
- physiological impact of music and sound on the human nervous system
relationship between frequency and pitch
frequency = acoustic concept
pitch = physiological concept
-highly correlated with each other
-higher frequency = higher pitch
relationship between intensity and loudness
intensity (physical features of sound; dBSPL)
loudness (physiological response toward sound intensity)
-higher sound intensity = louder sound
3 auditory tasks
- auditory sensitivity (detection)
- auditory discrimination
- auditory identification (recognition)
auditory sensitivity
detection
don’t need to identify the sound, just the stimulus
need to hear sound to perceive it
auditory discrimination
when you have 2+ sounds, you have to decide if they are the same or different
auditory identification
recognition
identify meaning of speech and understand the meaning it carries
ex: speech recognition
most important task
psychoacoustic methods
- method of limit
- method of constant stimuli
- scaling method
method of limit
how we measure the response to sound
- ascending and descending; adaptive
- fixed step size
- threshold: average of reversals
ascending and descending factors in method of limit
- ascending: start at a low level and bump up until a person can hear something (adaptive)
- descending: start on a higher level and go down until the person can’t hear anything
- some bias for descending bc the person has anticipation for the sound bc they have heard it before
- ascending is more conservative bc they can be sure of a heard sound if they start with none-
- do both–>combination of both gives a better threshold
fixed step size factors in method of limit
increasing or decreasing the sound by a fixed number every time
(5 dBSPL) 10–>15–>10–>15–>20
threshold/average of reversals factors in method of limit
- reversal = point at which the direction of sound changes
- point before and after the levels change
- to get threshold, you need to average reversals
- 7 reversals–>throw out first 3 and average remaining 4 to get reliable threshold
- threshold % is based on up, down rules
method of constant stimuli
- a # of stimuli ranging from rarely to almost always perceivable are presented one at a time and the subject responds to each stimuli (yes/no)
- equal number of stimuli at each level
- psychometric function–>plots % correct of auditory perception as a function of sound level
- threshold: a certain % point; lowest sound level we can hear
- measure at each level the % the listener gets correct–>usually creates an “S” shaped curve (curve is called psychometric function)
scaling method
- direct scaling: directly establishes the correspondence between physical sounds and their perception (loudness and pitch)
- ratio scale: compare target sound (given) to reference sound; used to tell how much louder the target is than the reference
- magnitude scale: no reference sound provided; just how you perceive the sound–>1-10 loudness scale; based on personal experiences
audibility
sound that is loud enough to be heard; basic sound detection
threshold of audibility
the lowest level of sound that is detectable with a certain %
factors influencing threshold of audibility
- sound frequency
- listening field: free field, inset earphone, headphone
- sound duration: temporal integration–longer sound is more energy = easier to hear; capacity to integrate sound energy at longer time
definition of frequency discrimination
our capacity to discriminate frequency change
lowest difference we can detect is 2Hz
definition of intensity discrimination
our capacity to discriminate intensity change
definition of duration discrimination
our capacity to discriminate duration change
frequency discrimination threshold
just-noticeable difference
depends on signal frequency and sensation level
-higher frequency, threshold goes up
duration (temporal) discrimination threshold
just-noticeable difference in signal duration
intensity discrimination threshold
just-noticeable difference
depends on signal frequency and signal level
as intensity increases, it becomes easier to detect and threshold goes down
masking definition
interference that one stimulus causes in the perception of another stimulus
how to define amount of masking (masking efficiency)
- amount of masking = performance in N (noise) - performance in Q (quiet)–>find the difference
- depends on frequency and level of the signal and masker
What can be a masker?
any unwanted sound
tonal masker
- sound that is a pure tone, such as a beep
- signal and masker are both tones
- masking efficiency is dependent on the intensity level and frequency of the tonal masker
noise masker
any other noise such as static, white noise, background speech, etc that interferes with the signal
psychoacoustic tuning curve (PTC)
- our auditory perception is tuned to the signal frequency
- most efficient masker has frequency that is identical to signal frequency
noise masking
- noise masker: broadband
- threshold: signal-to-noise ratio: signal level is how much above the noise level (signal level - noise level = ratio)
- affected by signal frequency, noise frequency, and noise level
auditory filter
- everyone has their own auditory filter
- filters out extra noise in order to perceive signals better
auditory filter bandwith
- measured by a notch-noise method
- equivalent rectangular bandwidth: the width of the rectangular shape–>convert triangle shape to rectangle with equal area
how to measure loudness
- matching method:
