Impact of Auditory Damage on Perception Flashcards
audibility of ___ phonemes becomes difficult
softer
degree of threshold loss is
disproportionate
The degree of threshold loss is disproportionate
what does this mean
Loss is typically greater in high frequencies while low frequency audibility is not as affected
what are the impacts of threshold loss on audibility
difficulty hearing softer phonemes
disproportionate threshold loss (HF loss is greater than LF loss)
listener perceives volume as loud enoug (LF) despite inaudibility of consonant sounds (HF) (I can hear people but i don’t understand them)
perception of how loud a sound is comes from
low frequency audibility
hearing deals with
volume and loudness
How much support does 2k Hz alone supply?
35% of speech intelligibility comes from audibility of speech signals at 2k Hz
high frequency audibility is critical for
speech understanding
Which frequencies contribute the most to speech intelligibility.
high frequencies?
95% of speech intelligibility comes from audibility of speech signals ranging from
500 to 5k Hz
35% of speech intelligibility comes from audibility of speech signals at
2 kHz
3k Hz and higher adds an additional
25%
when fitting HA’s we are focused on kHz range
500-5000
___% of word recognition is determined by speech energy between 500- 2000Hz
70
frequencies below 500 and above 5k provide different kinds of information that may be important to
spatial hearing & hearing in noise
linear amplification
An equal amount of gain applied to every incoming signal both soft and loud
Adds an equal amount of gain to soft, moderate and loud input levels
signal processing doesn’t take reduced dynamic range into consideration
nonlinear amplification
compression is added
Signal processing uses compression to increase intensity of soft signals while decreasing intensity of loud signals
Output signal is shaped into a reduced dynamic range by adding more gain to soft sounds and less gain to loud sounds
nonlinear is also called
automatic gain control
what is the role of compression
to decrease dynamic range of the signals in the environment so all the signals of interest can fit within the restricted dyanmic range of hi person
what is automatic gain control
applies different amounts of gain to different input levels
hearing aid is deciding the intensity of all the sounds arriving through microphone and it is automatically deciding to add gain (a lot, a little, take away) etc.
agc
what is dynamic range
Range from threshold to uncomfortable listening level
how does abnormal loudness growth occur
OHC damage results in loss of amplification of soft signals while IHC continue to detect louder signals
what is abnormal loudness growth
Individuals with threshold loss perceive sound shifting from too soft to too loud more rapidly
*complaint = increased sensitivity to loud signals
due to PT not hearing softer sounds because the amplifiers are gone and rapidly the sound goes from soft to too loud
result of reduce dynamic range
distance bw threshold and too loud becomes smaller
what is no recruitment
no loudness growth
separation stays even with loudness growth
what is partial recruitment
near normal fxn but not quite the same
complete recruitment
when we catch up with loudness growth to normal hearing
when we catch up with loudness growth to normal hearing
loudness growth
How do modern hearing aids manage frequency specific variations in a person’s dynamic range?
Amplification applies different compression ratios across frequency ranges to shape an output signal into a reduced dynamic range
done by manipulating compression in frequency shaping channels
what is multi channel compression
different frequency ranges
have gain for soft sounds and less for loud
what is compression ratio
how much is compressed bw soft and moderate inputs and moderate and loud inputs
why is there a lot of compressiokn around 2kHz
because we want more compression for speech
what is frequency resolution
Auditory systems ability to detect discrete frequencies in the cochlea
how does as detect discrete frequencies in the cochlea
Acoustic signal creates a traveling wave that results in one sharp peak on the basilar membrane at a point equal to the input frequency
Produces clearly defined vibration at one narrowly defined site along basilar membrane
what is meant by the bm is frequency specific
Tuned so that when certain bundle of cells are stimulated it will create one sharp frequency peak (tuning peak)
Ex: a 2000 Hz will always hear and stimulate the same place on the bm every time that sound goes in etc.
what supplies the frequency resolution needed for speech intelligibility in noise
sharp peaks
helps the healthy cochlea detect discreetly intense signals in narrow frequency regions within complex listening environments (i.e., listening in the presence of multi-talker babble)
frequency resolution
help us to hear in noise
sharp peaks
how do sharp peaks allow us to hear in complex listening environments
Sharp tuning curve peaks pierce through the noise differentiating the desired signal (speech) from the less desired signal (noise)
as you focus on a voice in noise, the sharp peaks allow to tune into certain things to understand speech
what is upward spread of masking
Intense low frequencies mask weaker higher frequencies
if basilar membrane can’t create a sharp audible tuning curve in higher frequencies than low frequency OHC amplification overwhelms audibility of softer HF signals
Why does reduced frequency resolution make it difficult to understand speech in noise?
once OHC no longer amplify soft signals the bm no longer has sharp tuning curves
because of this frequency resolution decreases causing the primary signal to no longer be enhanced and in turn makes it hard to determine the desired signal from the undesired signal
understanding is diminished because the brain cannot untangle the desired signal from the undesired noise
what is temporal resolution
as ability to detect small time changes in acoustic stimuli over time
why do we need good temporal resolution
needed to understand speech in noise
what can an awareness of time related cues help us to do
differentiate sounds that sound similar
what is gap detection
identifying the brief gaps or pauses between syllables, words, sentences, etc.
first temporal process
without it words form together
thresholds are typically between 2 and 20 milliseconds (ms)
spoon vs soon
what is phonemic duration
similar words are distinguished from one another by tiny differences in duration and order
can vs cant
what are time related cues examples
gap detection
phonemic duration
temporal ordering
suprasegmentals
what is temporal ordering
can we retai the order sounds come in or do they get mixed up
boots vs boost
VOT (longer for voiceless, short for voiced)
consonant duration - longer in boost
what are suprasegmentals
provide us with meaning (is it a question, demand, etc.)
patterns of stress, intonation rhythm
The _____ the gap detection threshold, e.g. up to 300 msec, the _____ the probability that a person will have difficulty with speech discrimination
greater, greater
what is an example of temporal resolution
time related cues
person having difficulty with speech discrimination in greater gap detection represents what abnormality
bottom up auditory processing disorder
what is temporal fine structure (TFS)
rapid fine oscillations providing info on timing in the temporal envelope
Supports detectioin of speech & nonspeech signals in noise
TFS
results in inability to extract information from the mixture of sounds conveyed bw rapidly fluctuating speech signal & noise
loss of ability to detect TFS
Supports vowel identification & consonant place of articulation
TFS
Cues are linked to melody/pitch perception and listening to speech in a competing background
TFS
what is temporal envelope
slow overall changes in intensity over time
slower amplitude modulations superimposed on TFS
creates and measures an outline of acoustic signal
cues are associated with speech perception in quiet
ENV
Helps to identify manner of articulation, consonant voicing, duration, prosidic cues
ENV
How will loss of audibility of tfs features impact speech intelligibility?
trouble understanding in noise
How will loss of audibility of ENV features impact speech intelligibility?
difficulty understanding in quiet
Current cochlear implant systems convey mainly _____ information in different frequency bands,
envelope
why might cochlear implantees have relatively poor ability to undrstand speech in noise
current CI systems convey mainly envelop information and env helps to hear with no noise whereas tfs helps us to hear in noise
Why do we need to know what a hA can and cannot do?
Signal processing in HAs may or may not be able to preserve both env (for understanding in quiet) & TFS (for understanding in noise)
Knowledge of signal processing tech is needed to determine which HA features preserve the critical info in the output signal
Spatial hearing allows us to/benefits of spatial hearing
Determine location of a sound source
Unmask sounds otherwise masked by noise
Brain combines and analyzes info arriving from both ears for improved signal detection & identification of speech in noise
Shift our attention and focus on one sound source while ignoring another
Feel connected with the environment
what is spatial hearing
ability of the as to determine the direction of a sound source
provides localization
auditory nerve (neural timing)
what is interaural timing differences
amount of time bw sound arriving to one ear to the other ear
what is interaural level differences
difference of volume bw two ears due to shadow effect of the head reducing intensity especially for higher frequencies
Which frequencies supply the most information on interaural level differences?
high frequencies (>3 kHz)
significantly affected by the geometry of the head, outer ears, and shoulders, which is why the patterns are much more irregular
ILD
nearly spherically symmetric around the interaural axis, are much less frequency dependent, are maximal for positions right off to one side of the head, and never exceed values of 700 microseconds
ILD
very frequency dependent
ILD
Which frequencies supply the most information on interaural timing differences?
low frequencies (<850 Hz)
identify spacial location & sound source
ITD
carried in fine structure of low frequency sounds and in envelopes of high frequency
ITDs
NOT as frequency dependent
ITD
Patterns are more predictable; more regular
ITDs
nearly spherically symmetric around the interaural axis, are much less frequency dependent, are maximal for positions right off to one side of the head, and never exceed values of 700 microseconds
ITDs
need audibility of low frequency cues for
timing differences
need audibility high frequency cues for
level differences
Reduction in sound level occurs for high frequency sounds for the far ear
The head casts an acoustic shadow
ILD
best for high frequency sounds because low
frequency sounds are not attenuated much by the head
ITD
Head shadow impact varies by
frequency
explain HRTF
HRTF is a response that characterizes how an ear receives sound from a point in space
pinna & head affects frequency intensities
measures in the ear canal show patterns of amplitude peaks & notches high frequency amps as sound arrives from different angles
What information do these monaural spectral cues supply?
the interaction of the pnna with incoming sounds depending on the sound source relative to the body provides these cues helpful in locating sounds occuring above or below and in front or behind us
impact of microphone position on the audibility of
monaural spectral cues
Does a discussion of audiometric thresholds sufficiently explain why a patient is experiencing communication difficulties?
no
this is because Audiologists tend to oversimplify diagnostic counseling by focusing on the sounds a patient can & cannot hear
Audiograms are not predictive of the activity limitations resulting from a hearing loss
How could an audiologist supply a patient with a better understanding of their auditory rehabilitation needs during post diagnostic counseling?
