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67 Cards in this Set
- Front
- Back
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Psychoacoustics
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the study of psychological response to acoustical stimulation.
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threshold
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an intensity above which an organism always responds, and below which an organism never responds.
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External factors affecting threshold
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procedural limitations, instrumentation, sound proof testing environment
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internal factors affecting threshold
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attention span, biologic noise
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MAF
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2 ears,
sound field loudspeaker shape of head, pinna effect |
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MAP
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1 ear
probe microphone poorer in lower freq bc of internal noise trapped in ear canal bc of probe mic poorer in high freq bc middle ear characteristics/calibration of equipt. |
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threshold of pain
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120-130
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MAP high and low tones
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sennheiser and TDH respectively
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stimulus duration
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longer duration=lower threshold
10-200 ms 200+ nothing -10 other more dectable freq may catch notice |
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JND
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smallest change in a stimulus that is detectable
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webers law
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change in stimulus/starting point of stimulus
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frequency discrimination
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freq less or = 1000 Hz need 1-2 Hz change.
freq 4000 need 11-15 change freq 5000 need 20-25 change |
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intensity discrimination
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from 250-8000 Hz need .5-1 dB
closer to threshold = larger JND |
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Gap detection
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4 beeps shown. are gaps btw 2 different beeps same or diff?
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masking
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shift in threshold of 1 tone bc of a masking tone
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upward spread of masking
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its hard to mask lower frequencies because of the tonetopic organization of the cochlea.
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S/N ratio
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the ratio needed to mask changes as a function of freq
(level needed to hear signal over masker) |
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increase freq means
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u increase the signal to noise ratio
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Fletchers hypothesis
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critical band masking
internal filter helps determine the detection of a signal in noise. |
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critical band
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frequencies within the passband of the internal filter critical for masking
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notch noise
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noise bans are on each side of the internal filter.
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as spectral notch gets bigger in Hz
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less noise energy goes through the internal filter. wider notch= easier to hear
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backward masking
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signal b4 masker (backwards because its easier and psychoacoustitions like harder better ;))
need 50 ms |
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forward masking
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signal follows masker
need 75-100ms |
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clinical masking
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eliminate the influence of hte better ear
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why are 2 ears better than 1?
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10log 2:1
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localization vs. lateralization
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sound in space-
fused image in head |
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270
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azmuth=left
vertical=butt |
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Interaural differences?
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ITD
ILD IPD |
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ITD
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independent of freq
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ILD
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High freq stim. bc of head shadow effect
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IPD
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vary with freq.
around 2000 Hz is hard because head is 22-23 cm in length and takes .6 ms to reach |
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MAA
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smallest angular seperation between two stimuli that a listerner could detect
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Precedence Effect
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ITD wins!
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Head Related Transfer Functions
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Italian Barber Shop
measure acoustic spectrum present this stimulus under earphones |
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monotic
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stimuli= one ear
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diotic
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identical stimuli to both ears
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dichotic
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different stimuli to two ears
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MLD
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difference between a dichotic listening situation and a monotic listening situation.
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MLD is
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15 dB at 50-0 Hz
and 2-3 dB at 2000Hz |
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Cocktail Party Effect
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You get a 15 dB improvement for a over a monotic listening situation with a dichotic listening situation
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loudness vs intensity
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loudness is a persons perception of intensity
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loudness level is measured
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in phones
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40 phones (baseline) equals
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1000Hz tone at 40dB SPL
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Loudness measured in
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Sones
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1 sone equals
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40 phons
(use for 2ice loudness or half loudness of reference stim) |
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our perception of double loudness is
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only 10 dB more
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90 dbA
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weighting scale of A = least of ABC
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dynamic range
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the range in which u can hear. adaptation
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pitch
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perception fo frequency
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Pitch is measured in
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mels (mel super sexy stephens pitches well)
NOT EQUAL TO HERTZ |
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Level Effects on Pitch
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3000+ increase in level= +pitch
1000-3000= constant level/pitch -1000 more level=less pitch |
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Missing Fundamental
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300,400,500,600,700 Hz presented
tone percieved is 100 Hz bc the period lasts for 10 ms |
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timbre
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differentiation between 2 or more sounds that have the same pitch, loudness, and duration (trees)
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consonance vs dissonance
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pleasant perception
unplesant perception |
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density
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increases as frequency/intensity increases (i have a very dense voice when loud)
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volume
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increases with low intensity and low freq.
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Lowest Exposure Levels of Noise
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stereocilia swell/fuse
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Low Exposure Levels of Noise
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OHC's damaged
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High Exposure Levels of Noise
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all damaged (stereocilia, tectorial membrane, basiliar membrane)
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TTS
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returns 2 preexposure levels
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PTS
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hearing loss
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Noise stimuli factors
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level/duration
TTS will occur at Freq of stimulus For higher levels, TTS occus at 3000-6000Hz |
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tinnitus
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constant annoying noise in ear- some mechanical energy is caught along the basilar membrane stimulating the hair cells
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loudness recruitment
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rapid growth of loudness as level is increased
abnormal sensitivity dynamic range shortening... |
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hypothesis for loudness recruitment
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1. reduced Hz selectivity
2. destruction of OHC's meaning less low level signals while high signals are the same. |
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Psychophysical Tuning Curves
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Loss of OHC's = no sharpness (loss of freq selectivity- bad freq resolution)
IHC loss= Higher thresholds |
