Quiz 1 Review (Part 2) Flashcards
3 parameters allowing the brain to recognize sound?
pitch intensity and time
what is pitch
subjective or perceptual attribute that corresponds closely to the physical attribute of frequency
A change in frequency is heard as a change in
pitch
can we measure pitch
not diretly
measured by matching the pitch in question
what is pitch related to
the physical repetition rate of the waveform of sound
Increasing repetition rate = sensation of increasing pitch
How do we know if something is high or low pitch
More vibrations in a given time = high pitch
Less vibrations in a given time = low pitch
what the audiometer is testing
frequency
perception we hear
pitch
what is frequency discrimination
ability to detect changes in frequency
Normal hearing in humans can differentiate as low as 3 Hz difference
Discriminate between 2 sinusoids that are simultaneous with a brief interval between them
Ex → 1000 Hz sinusoid can just be differentiated (just noticeable difference-jnd) from a 1003 Hz sinusoid with a silent interval between them
what is frequency selectivity
ability to resolve complex sounds into its component frequencies
Not the same as discrimination
Complex sounds: speech, music etc.
The cochlea achieves frequency selectivity through its structure, where different parts respond to different frequencies (higher frequencies at the base, lower frequencies at the apex).
“tuning” of the cochlea.
Example → When listening to a conversation in a noisy environment, frequency selectivity helps us focus on the frequencies of the speaker’s voice while ignoring background noise
ability to separate or filter out specific frequencies from complex sounds.
selectivity
ability to notice small differences between two sound frequencies.
discrimination
what are the pitch perception theories
place theory
temporal/volley theory
what is the place theory
explains how we perceive different pitches (the highness or lowness of a sound) based on where sound waves stimulate the cochlea
Both discrimination and selectivity are closely connected here
what is frequency place mapping
explains how specific sound frequencies are linked to precise locations along the cochlea → helps us understand how our brain decodes different pitches based on where the cochlea is activated
A high-pitched sound causes maximum vibration at the _____ of the cochlea
base
A low-pitched sound causes maximum vibration at the
apex
suggests that our perception of pitch is linked to where in the cochlea the sound waves create the most activity and that specific places correspond to specific pitches.
place theory
how does the place theory work
Specific Regions of the Cochlea → The cochlea is “tonotopically organized,” (different parts of it are sensitive to different frequencies (pitches)). The base of the cochlea (closest to the outer ear) responds to high-frequency sounds, while the apex (the inner tip) responds to low-frequency sounds.
Pitch Perception → the pitch we hear is determined by the specific location (or “place”) along the cochlea where the sound waves cause the strongest vibrations, the point of maximum displacement in the traveling wave
Place Theory suggests that our perception of pitch is linked to where in the cochlea the sound waves create the most activity and that specific places correspond to specific pitches.
true
what is the temporal/volley theory
explains how we perceive pitch, especially at lower frequencies, based on the timing of neural firing rather than the specific location of activation along the cochlea
Auditory neurons phase lock to vibrations of the BM
Pitch assigned to a signal is determined by the timing pattern of neural impulses evoked by a stimulus
When LFs are heard, neurons fire at a particular phase of the waveform so that the neural spikes are at or close to the integer multiples of the period of the pure-tone
Different frequencies produce different patterns of neural spikes across time
how to determine timing of a tone
T = 1/f x 1000
500 Hz pure tone
t= 1/500 = .002 x 1000 = 2 ms
550 Hz pure tone
t= 1/550 x 1000 = 1.8 ms
Information from timing cues breaks down at around
5 kHz
how is pitch
determined in complex signals
There are many different frequencies but only one dominant pitch
The pitch above is matched ot a 100 Hz tone = fundamental (f0)
Pitch perception of harmonic complexes are explained by either ____ or ______
place or timing
how is pitch perception explained by place
max energy at 100 Hz causing excitation at the place corresponding to 100 Hz
how is pitch perception explained by timing
time-domain waveform could be periodic with a period equal to 1/f0 (t = 1/f)
to find period 1/f
to find frequency 1/t
other terms for missing fundamental
virtual pitch or residue pitch
what is the phenomenon of the missing fundamental
First tone that is heard has all of the frequencies, second tone has the fundamental removed but keeps all of the higher harmonics, each one after removes the lowest harmonic but although each note changes the pitch remains the same
this happens because they are harmonics and complex signals so they have the timing consistent with the fundamental even without it being present in the signal
Even though the fundamental frequency was removed from the signal the pitch perception stayed the same due to the brain interpreting the repetition patterns (harmonics-periodicity) that is present
what could or could not explain the missing fundamental
Cannot be explained by place theory because excites BM at that fundamental but now that the fundamental is gone it doesn’t explain how we still pick up the pitch so volley explains this
Could be explained through temporal theory because even though the fundamental is absent the temporal pattern of neurological activity is related to the period that is still being detected
what is cochlear HL associated with
reduced frequency selectivity (broad auditory filters)
When a sound contains multiple tones it is harder to tell them apart when there are a moderate number of them, making it more challenging to understand speech clearly or appreciate music
true
why do people with HL for a while think they are fine and can understand?
they have memory, context, etc.
but out of context they will have a hard time
what do PTs with cochlear HL rely on
depend on temporal cues and less on spectral information due to reduced frequency selectivity from the broad auditory filters
Those with cochlear loss have variable results even with similar audio results due to
individual differences in auditory filter size
neural synchrony
when do cochlear loss PTs have good pitch disrimination
Well preserved neural synchrony
when do cochlear loss PTs have poor pitch disrimination
Poor preserved neural synchrony Regardless of degree of the cochlear loss (broadening of the auditory filters)
Pitch is important in order to understand
language
Pitch perception is important to
Distinguish most important utterances in speech
This is why those with HL have issues understanding unless there is context
Indicate structure of sentences of phrases, especially for tonal languages (e.g. Mandarin, Chinese, Thai)
Convey nonlinguistic information
Gender, age and emotional status
Supplement speech reading
Voicing information is helpful (seeing your mouth etc.)
what is temporal resolution/acuity
how the as processes time-varying information changes
what is gap detection
Ability to detect changes over time between two brief stimuli
two main processes of temporal resolution
Within-channel gap detection threshold
Across-channels gap detection threshold
what is within channel GDT
minimum time needed to detect a gap between sounds that have the SAME spectrum
Within each frequency filter you can detect the timing changes (close frequencies)
what are channels
filters in the cochlea
if there is a larger gap
harder time understanding speech
if you have two sounds in the same spectrum and they are separated, how far apart in time do they need to be for the brain to recognize they are different?
3 ms
what is across-channel GDT
minimum time needed to detect gap between sounds presented to two ears
sounds that are spectrally dissimilar (e.g., tone and noise)
able to detect that sounds are two different ones
what are the differences between within and across
w/in: relies on detecting a temporal gap in a single frequency channel
Across: requires integrating information from multiple channels making it more complex and usually yielding higher thresholds
what is temporal integration/summation
Ability of the as to add information over time
if the sound is heard for a short time it will be harder to hear than one heard for a longer time
auditory system appears to integrate pure tone signal over
200-300 ms period
Auditory thresholds do NOT improve if the signal duration >300ms
true
If stim duration is too long (e.g., 2 min) threshold may become worse due to
adaptation
neurons will stop firing when the tone has been on for too long
Sounds are characterized by pressure variations over time
true
intensity and frequency are constant over time
steady sound
what processes are used to measure temporal resolution
GDT
Temporal masking
amplitude detection
determine the smallest detectable time gap between two stimuli
GDT
what signals are used in GDT
sinusoids, BBN, or NBN
GDT in humans of clearly audible noise bursts. is
about 2 to 3 ms
GDT increases for frequencies < 200 Hz
three types of GDT
simple paradigm - silent variable time gap between two signals (e.g. Random GDT)
2nd Test used → two or more signal pairs with one signal containing a variable silent gap
3rd Test used → series of BBN segments with 0-3 gaps per segment varying in duration (e.g., GIN → Gaps In Noise test)
what is the amplitude modulation detection threshold
determine the smallest amount of variation needed to detect that a sound is fluctuating in level → smallest amount of variation to recognize that it is varying and not steady
closer the cycles are together =
faster amplitude modulation rate
deep amplitude modulation depth =
far from baseline, large modulation depth
farther apart the cycles are together =
slower amplitude modulation rate
shallow amplitude modulation depth
close to baseline, small modulation depth and brain cannot grasp it so it has to be louder
Temporal modulation refers to a
recurring change (amp or frequency change over time)
temporal modulation is important because
speech is a modulating signal
degree of change determines _________ of signal
modulation depth
The depth of modulation is dependent on the ______ of the stimulus, which is the frequency at which the modulation changes over time
rate
what is rate of a stimulus
frequency at which the modulation changes over time
Ability to detect modulation worsens at ______ & ________ as modulation rate increases. What is then needed?
low SLs and higher frequencies
Greater modulation depth is then needed for detection
what is the difference between simulataneous and non-simultaneous masking
audio masking → simultaneous masking (masking occurs when signal and masker overlap in time)
non-simultaneous masking (forward and backward masking)
what is meant by temporal masking
masker and signal are separated in time
what is forward masking
masker comes first, then the signal
Short duration signal masked by louder sound closely preceding it
For signal detection, separation between masker and signal needs to be >100-200 ms
Masking occurring is forward in time
Signal duration is short
Masking duration is longer
what is the theory behind forward masking
when you have a large signal the neurons are firing and then once they fire they have a refractory period so it takes them time before firing again and because the masker is so loud and large, they fire and are refractoring and at this point the tiny signal comes in and is not enough to restimulate them because they are in the resting phase
no matter your hearing sensitivity you will not be able to hear the signal
this disappears within 100-200 ms so after the masker turned off, if a signal is put in it will not be heard but after this time period the signal will be heard
if you have a longer and bigger signal than the masker you
will hear it even within the 100-200ms
if you have a long masker and short signal and wait 1-2,
you will hear it
if you have a long masker and short signal and do not wait 1-2,
you will not hear it
what is backward masking
signal comes first then the masker
Short duration signal masked by a sound rapidly following it
For signal detection, separation between masker and signal has to be >25-50ms
Masking that occurs is backwards in time
Signal duration is short
Masker duration is longer
in true forward and backward you will not hear the signal
true
why is backward masking backward
Backwards because the signal is already there when the masker comes in
same criteria as forward but different timing
binaural
sound reaches both ears
diotic
identical stimuli presented to both ears
One signal in both ears
E.g., speech and speech or noise and noise etc.
dichotic
sound presented to two ears is different
Two different signals in both ears
E.g., tone and noise or speech and noise etc.
localization
judgement of sound position outside the head
lateralization
judgement of sound position within the head (under headphones)
Listening to sound under headphones
what is the duplex theory of sound localization
explains how we locate sounds in space using two main auditory cues: interaural time differences (ITDs) and interaural level differences (ILDs). these cues are used differently depending on the frequency of the sound
There are two sound cues used for localization
ITD or IPD (phase)
Provides localization for LF stimuli
ILD
Provides localization information for HF stimuli
Localization is better for complex stimuli than for pure tones
Wavelength is inversely proportional to frequency
true
difference between ILD and ITD
ILD
HF cue
HFs have shorter wavelengths and are about the size of the head, producing a sound shadow (good cue for sound localization)
Cue can be as high as 15-20dB
Head shadow effect
HF waves are partially blocked by the heat creating a difference in loudness between the ears
ITD
LF Cue
Sound wave’s longer wavelength reaches both ears at slightly different times and can transfer over the head
Comparing the phase differences arriving to each ear
When wavelength of sound wave is smaller than the diameter of the head (> 1500 Hz), an ITD is
greater than one period of the wave
Here, comparing phase differences between waves arriving at each doesn’t provide a unique ITD
Sound stimuli in front of a listener (00 azimuth and elevation) produce no interaural differences. why? what neurons are the most sensitive here
There are no interaural differences because the sound is not on either side
midline neurons are the most sensitive here because you have to pick up the signal from the front since l and r ears are not getting cues due to no differences
ITD Cues & MAA
MAA is smallest when sounds come from directly in front
When reference ITD is at 00 azimuth
</= 900 Hz MAA = about 30
up to 900 Hz if the sound is only 3 deg apart you can detect the sound source changed using ITD cues
for <900 Hz in the LF you can notice a change in angle by 3 deg with the help of ITD cues
900-1500 Hz MAA = thresholds increase dramatically
Doesn’t do a good job; not as sensitive here
>150 Hz MAA = undetectable and cannot be used to detect MAA for sinusoids
after 1500 it is hard and you lose these cues which is because it is good for LF
for <900 Hz in the LF you can notice a change in angle by 3 deg with the help of ITD cues
true
after 1500 it is hard to use ITD cues and you lose these cues which is because it is good for LF
true
ILD cues and MAA
MAA is smallest when sounds come from directly in front
When reference ILD is at 00 azimuth
ILD changes can be detected across frequencies when azimuth is > 00 azimuth but practically they are sufficiently large only at high frequencies
Performance worsens around 1500-1800 Hz
Due to small wavelengths compared to head diameter
we do not do good at localizing above 1500 Hz with both ILD and ITD cues
we can still do it we just need more separation
true
why are binaural beats important
they add another cue and richness to the sound for localization and signal detection
When tones are in phase
add
When they are out of phase
subtract
When two signals with frequencies very close to each other are presented, what are produced
beats
what are beats
waxing and waning of a signal
what is the binaural beats
auditory illusion that occurs when two slightly different frequencies are played separately into each ear. The brain perceives a third, “phantom” beat frequency that is the difference between the two tones. For example, if a tone of 300 Hz is played in the left ear and a tone of 310 Hz in the right, the brain perceives a 10 Hz beat (310 - 300 = 10 Hz).
equation for beats
Number of beats/second = | fS2 - fS1 |
If difference between frequencies = 3 Hz; waxing and waning will occur every 3 times/s
If difference between frequencies = 5 Hz; waxing and waning will occur every 5 times/s
amplitude vs. time
beats
when will beats not be heard
signals are the same frequency because they are always in phase so there is no addition or cancellation of signals (no beats)
If the difference between signal frequencies is >50-100 Hz
Time difference here allows the brain to detect the two signals as separate pure tones with different frequencies (no beats)
what is the importance of sound source determination
Want to be able to do this when for ex you want to focus on one person talking and there are others talking in the background
sound source determination uses
Perceptual coherence
Precedence effect
Modulation Detection Interference (MDI)
Comodulation Masking
Binaural Masking Level Difference (MLD)
what is perceptual coherence
Components of speech are grouped together and perceived as one auditory event
How does our brain pull together the same sounds
when will perceptual coherence more likely occur
if the components have similar acoustic properties like
Common fundamental frequency (f0)
The same voice onset time (VOT) - When VT is blocked for a stop consonant and a vowel follows
Measurement of the time between the release of the stop and start of the voicing
VOT is only applicable to stops and no other sounds
Sound from a single source generally sounds the same regardless of whether presented in isolation or presented with other sounds
true
what is the Precedence Effect/Law of the First Wavefront
llusion produced when 2 similar sounds are delivered in quick succession from sound sources at different locations but only a single sound is perceived
Why we do not here in echoes even though they are present
echo threshold
30 to 50 ms for complex sounds
before we hear the echoes
Law of the first wavefront states
We localize based on the signal that reaches our ears first
whichever wave hits your ear first will be the location that the brain says where sound is coming from because it suppresses the sounds that come in quick succession
what is echo suppression? how do we perceive it in forward and backward recordings
Binaural auditory systems tend to suppress later-arriving sounds (echoes) and emphasize the first wave front (indicating sound source location)
We can hear echoes a microphone picks up when we play recordings backwards
We do not hear the echoes in real time because of echo suppression
Changes in voice quality are noticed when recordings are played forward and the reflections are not heard as echoes but more subtly these changes
Localization is better for pure tones than complex tones
FALSE
it is better for complex stimuli than for pure tones
do pure tones cross filters
no
do complex signals cross filters
yes
modulated vs unmodulated signals
modulated: loudness of the sound fluctuates periodically. This modulation can make the signal sound like it’s “pulsing” or “wavering,”; will cause an increase in threshold by 10-15dB; complex sounds
unmodulated: has a constant amplitude, frequency, or phase throughout its duration. this makes it sound steady and unchanging to the listener; pure tones
When masker and signal modulator frequency are similar, threshold for detection of the amplitude modulated signal increases (worsens)
true
Similar masker and signal modulator frequency (even in different filters) =
threshold for detection of the amplitude modulated signal increases (gets worse)
This is because the masker masked the signal
Different masker and signal modulator frequency =
threshold for detection of the amplitude modulated signal decreases (improves)
They are in different filters so you will hear both
what is comodulation masking release
Phenomenon which the detection of a tone centered in a modulated band of noise is improved with the addition of another band of modulated noise
Detection of a tone masked by a modulated noise will improve significantly if another band of noise with the same temporal characteristics is added
we added a modulated masker and the signal threshold went down (supposed to happen) but now along with this masker we add another modulated signal the threshold gets better and comes down
what is this phenomenon
Comodulation Masking Release
why does tone detection improve with two added maskers that are similar?
Detection of the tone improves because the two modulated bands of noise are perceptually grouped by the CANS while the signal is detected as a separate auditory event - perceptual coherence
what is the difference between MDI and CMR
MDI - one masker and one signal, causes poorer threshold because it masks
CMR - one signal, two maskers, causes better thresholds because the brain lumps the two together
Perceptual coherence causes CMR to happen
what is the Auditory Scene Analysis/Cocktail Party Effect
Ability to focus one’s listening attention on a single talker among a myriad of voices and background noise
AS breaks down sound waves into different frequency components using spectral analysis of the cochlea & after separating sounds this way it can assign different
Factors aiding listening in a complex listening situation
Spatial separation
Voices coming from different directions
Where are the voices coming from
azimuth
Different pitches of different speakers
Men, women, children etc.
Different f0 of speakers (male vs. female differences)
We all have different ones based on how the VFs vibrate and this is why our voices are so distinct
Different accents
Different speeds of sound reaching the ears
Localization: how long does it take for the sound to hit you
Farther away - softer voice
Closer - louder voice
Masker and signal coming from the same side
difficult listening environment
Masker and signal coming from separate sides
easier listening environment
what is auditory figure ground
ability to focus on a specific sound or “figure” in a noisy background, which is the “ground”
Figure = sound you are paying attention to
Ground = any other sound
what is binaural masking level differences
Phenomenon where listener’s ability to detect a sound signal in the presence of background noise improves when using both ears rather than one
observed when there’s a phase or time difference between the signal (e.g., a tone) and the noise in each ear
allows us to hear in noisy environments and localize based on phase changes
Binaural Masking Level Differences (MLDs)
release from masking
Listener listens to a tone and noise identical in both ears, the level is adjusted until the tone is no longer heard (masked), and the signal is phase shifted 180 deg out of phase to make the tone audible again
