midterm 2 Flashcards
how to find dB IL
dB IL = 10log (absolute / reference)
how to find dB SPL
dB SPL = 20log (absolute / reference
what is the reference for IL
10^-12
what is the reference for SPL
20
an increase of tenfold is represented by an increase of how many dB SPL
one tenfold = 20 dB increase
filter
how a system changes a sound
-device that changes a sound by attenuating and/or damping sounds
-how does it change as it goes through
process of a filter
initial input, inputs into filter, transfer function, and output is taking form of the input with the filter
examples of filters
microphones, headphones, and earplugs
transfer function
the function that a filter does
center frequency
the center point of a curve
-where the most energy is
upper cutoff frequency
point along the down curve that is 3dB below the peak
-on the right of the center frequency
lower cutoff frequency
point along the up curve that is 3dB below the peak
-on the left of the center frequency
bandwidth
the range between the upper and lower cutoff
-the wider this is, the stronger the sound will be
rejection rate (attenuation rate)
change of decibels per octave
-octave being a double of frequency
low-pass filter
allows the lows to pass through
-filters out the high frequencies
-will have an upper cutoff
-slopping down
high-pass filter
allows the highs to pass through
-filters out the low frequencies
-will have a lower cutoff
-slopping up
band-pass filter
filters on either side
-has a range
-upper and lower cutoff, rejection rate, and center frequency
constant percentage bandwidth filter
the bandwidth is a percentage of the center frequency
-a type of band pass filter
band-reject filter (notch filter)
passes almost all sound except a very brief range of sound that it does not allow through
-discrete or wider missing area
-constant level with a dip down
how to calculate the sound pressure level
SPL = Lps + 10logBW
-Lps : pressure spectrum level
-BW : bandwidth
overall sound pressure level (SPL) is
comprised of all the frequencies within a certain bandwidth
absolute sensitivity
lowest sound to just detect the presence of a stimulus
typical thresholds for human hearing
20 - 20,000 Hz
-below 20 Hz would not be perceived as a tone
-most sensitive from 1,000 to 5,000 Hz
minimum audible field vs. pressure
sound field vs. under headphones
dynamic range
the range between the softest audible sound and loudest tolerable sound
-threshold of hearing to threshold of discomfort, uncomfortable listening level and loudness discomfort level
typical dynamic range for human hearing
generally 90-120 dB SPL
-the difference is the dB number
threshold microstructure
these are the smaller frequencies in between marks
-we test discreet ranges and connect those dots
assumptions made when testing only at certain frequencies
we assume the threshold is whatever corresponds within the line between the two dots
-assumptions for it being a straight line
why are cochlear nonlinearities responsible for low auditory thresholds
outer hair cells within a typically functioning cochlear cause these low thresholds
-with a fully functional cochlear, these low thresholds occur
the cochlea is ….
tonotopic and nonlinear
tonotopic
each region along basilar membrane is sensitive to a certain frequency
-base of cochlea is high frequency
-apex (top) is low frequency
cochlear amplifier
how the various parts of the ear work together to amplify sound to the cochlea
what part of the cochlea is the cochlear amplifier
outer hair cells
linear input-output function
gain is the same at all points along the function
-input = output
what is gain
difference between the input and output
nonlinear (compressive) input-output function
gain differs at different points along the function
-input range does not equal output range
how to convert dB SPL to dB HL
dB SPL = dB HL + RETSPL
how to convert dB HL to dB SPL
dB HL = dB SPL - RETSPL
dB SL (sensation level)
a difference value between presentation level and the patients threshold
- presentation minus individual threshold = dB SL
sensation
sensory receptors detect sensory stimuli
-the physical process
perception
organization, interpretation, and conscious experience of those sensation
-requires a response
-psychological process
relationship between sensation and perception
sensation needs to occur for perception, but just because you have sensations it does not mean you will perceive it
4 auditory skill levels
detection/awareness, discrimination, identification, and comprehension
two categories of sensitivity
absolute and differential/relative sensitivity
absolute sensitivity
least amount of something that can be detected
-detection or awareness
-absolute threshold, threshold of hearing or the threshold of audibility
differential or relative sensitivity
least amount of change needed to detect a difference
-discrimination
-differential threshold, relative threshold, just noticeable difference (jnd), or difference limen
what do we mean by threshold is a probability
the probability for a response changes as the stimulus increases but below the established threshold, there is still some probability of a response and above the established threshold, there is a probability for no response
-there is no single point below which there is always no response and above which there is always a yes response
psychometric function
basis for all threshold measures
-y axis is the percentage of times they recognized the signal at the coordinating intensity
-above the threshold they responded more than 50% of the time
-plot based on responses at various stages
how to find the threshold on a psychometric funtion
draw a line over from the 50% response on the y, and the coordinating dB level at that point of the line is the threshold
what is the clinical percentage used for threshold
50%
5 parameters for measuring thresholds
method of presentation, starting level, step size, stopping rule, and how the threshold is defined
what is important for measuring threshold
-test validity : ensure to measure what we think we are measuring
-understand stimuli : present distortion and potential noise alongside with test stimuli
-distinguish between sensory capability and response bias
factors that influence response
attention level, motivation, understanding of the task, responding to something else, internal criterion, error of habituation, and error of anticipation
error of habituation
tendency to continue with previous response
error of anticipation
tendency to respond before detection because presentation of stimulus is expected
method of constant stimuli
stimuli is presented in random order
-pre determined, random order, with many presentations at each level
method of limits
stimuli are presented at predetermined starting points
-ascending (start below estimated threshold and go up) and descending (start above estimated threshold and go down) runs
-stop when response is obtained and start a new run
-equal number of both runs!
method of adjustment
stimulus is controlled by subject
-level change is continuous rather than in discrete steps
-move something until you hear a sound or turning a dial according to a sound
adaptive procedure
subsequent presentations depend on subjects response
-staircase method : with every response go down, with no response go up
-bekesy’s tracking method : play an increasing sound with the patient pressing a button and they release it when they can no longer detect it
direct scaling
subject is asked to establish a relationship between a standard stimulus and a comparison stimulus
-the relationship between two sounds
4 types of direct scaling procedures
magnitude estimation : assigns values to other stimuli based on the reference value
magnitude production : matches the other stimuli to a number based around the reference
ratio estimation and production : patient is asked to describe the relationship between two sounds within a ratio
cross modality production : patient is asked to express the perceived magnitude for one sense in terms of another sense modality
signal detection theory
psychoacoustic technique used to understand how decisions are made in ever-present uncertainty
-use for understanding how people respond to thresholds
-differentiate signal from noise
outcome table aspects
hit : stimulus is present with a yes response
false alarm : stimulus is absent with a yes response
miss : stimulus is present with a no response
correct rejection : stimulus is absent with a no response
internal criterion
something internally that triggers the response
-everyone will have these
liberal criterion
more hits, fewer correct rejections
-more likely to say yes
-can shift by giving a louder sounds so they remember what to listen for or stopping if they are just pushing the button
conservative criterion
fewer hits, more correct rejections
-more likely to say no
-can shift by indicating that you can tell that they are waiting for it to get loud before responding
how can criterion be shifted
-reward true positives (hits) and correct rejections
-punish false positives and false negatives (misses)
differential sensitivity
measurement of the just noticeable difference
-along a single dimension of a stimulus
-difference limen (DL), differential sensitivity
absolute differential sensitivity
the difference between two sounds
-least amount of something
relative differential sensitivity
found by taking the absolute difference divided by the values of the starting level
weber’s law
states that the value of the relative difference is a constant regardless of the stimulus level
-as the size of the original stimulus increases, the jnd increases
differential sensitivity for intensity and frequency depend on ______ and _________
presentation level and presentation frequency
the cochlear is a complex and _________ system
nonlinear
jnd for intensity
1 dB or better
-depends on presentation level
jnd for frequency
approx. .5% of the frequency
jnd for duration
as short as 2-3 msec
loudness
the perception of intensity
-remember intensity is the physical magnitude of a sound
-low intensity is a soft sound
-high intensity is a loud sound
equal loudness contours
using 1,000 Hz as a reference and will play various sounds and would match it as they go
-individual lines will be perceived as the same loudness at each point
-comprised of phon’s
phon
relates loudness at other frequencies to loudness at 1,000 Hz
-a unit of loudness perception to the reference of 1,000 Hz
how to find the phons given a presentation level (for a given frequency)
match the frequency to the presentation level and find the coordinating phon
-can be a phon level in between two of the main curves
how to find the presentation level at a given phon (for a given frequency)
match the frequency and phon level and trace over to the presentation level
sone scale
the relationship between loudness and intensity determined with direct ratio scaling
phon scale vs. sone scale
phon : relates loudness at other frequencies to loudness at 1,000 Hz, no relationship among phons is implied
sone : loudness relationships at the same frequency changing by level, 2 sones twice as loud as one
dB change for doubling of intesnity
+3dB
dB change for doubling of pressure
+6 dB
dB change for doubling of loudness perception
+10 dB
how to draw the loudness growth function for typical hearing
bigger increase at the beginning then a steady increase near the end
-extends the whole length of our threshold
how to draw the loudness growth for conductive hearing loss
same shape as normal hearing but there is a complete shift for the amount of HL there is
how to draw the loudness growth for cochlear hearing loss
start at the level of HL and there is a rapid increase
-same ending spot as normal hearing
recruitment
same term for classic model
-in relation to the rapid growth of loudness with a cochlear hearing loss
what is the minimum presentation length of a pure tone to ensure valid testing
200 msec
