Binaural hearing Flashcards
are hearing thresholds perfectly symmetrical?
rarely
Is research conducted binaurally?
no, monaurally
binaural fusion
separate signals from each ear are perceived as one fused auditory image
brain puts info from both ears and hear it as one single image
binaural summation
The ability to improve perceptual performance on a psychoacoustic task when both ears receive input
about 3dB
effect is hearing sounds louder
Imagine you have a patient with symmetrical hearing loss (same threshold at both ears). They come to your office wearing one hearing aid because the second one is broken. They tell you that the overall volume is comfortable with the one hearing aid in. You fix their other hearing aid and set it so both hearing aids have the same settings. Will the set of hearing aids still be comfortable or will adjustments need to be made?
yes they would because it would be too loud (as summed input from both sides making it sound louder) (summation)
If you had a patient with symmetrical hearing thresholds and you fit them with hearing aids providing the exact same amount of amplification, would there be a difference in loudness perception if the patient wore only one or wore both of the hearing aids? Explain your answer.
Yes, it would be almost twice as loud with both of the hearing aids in, due to binaural loudness summation
What would happen if you were testing hearing and discovered you had sound going into both headphones? Would this affect hearing thresholds?
yes because their thresholds would show as lower
improves thresholds in both noise and not
What plane is being referenced with the term “azimuth”? With the term “elevation”?
Azimuth = horizontal plane
Elevation = vertical plane
Describe the 0o azimuth, relative to a person’s head
right in front
Describe the 90o azimuth, relative to a person’s head
directly to the right
Describe the 180o azimuth, relative to a person’s head
directly behind
Describe the 270o azimuth, relative to a person’s head
directly to the left
Describe the 0o medial, relative to a person’s head
directly in front
Describe the 90o medial, relative to a person’s head
directly above
Describe the 180o medial, relative to a person’s head
directly behind
How do interaural level differences (ILD) arise? Draw a schematic. Is this a low frequency or a high frequency cue for sound source localization?
ILD’s arise because of the head shadow. Sound is reflected off of the head and casts an acoustic “shadow” on the opposite side. The sound level is greater on the side where the sound originated. This is a high frequency (above 1500 Hz) cue for sound source localization. See separate schematic.
How do interaural timing differences (ITD) arise? Draw a schematic. Is this a low frequency or a high frequency cue for sound source localization?
ITD’s arise because a sound arrives to one ear sooner than it arrives to the other. This is a low frequency phenomenon (below 1500 Hz). See separate schematic
Where is ILD greatest?
90 azimuth
where is ILD smallest?
0 azimuth because it is directly in front and going to both ears the same
does the monaural system do much with phase differences?
no, the binaural system
what does head related transfer function (HRTF) do?
describes the spectral characteristics of sound as measured at the tympanic membrane when the sound source originates in 3D space
Is HRTF a monaural or a binaural sound localization cue?
TF is a monaural sound localization cue in the vertical plane
Is this cue (HRTF) effective for narrowband or broadband signals? Why?
effective for broadband signals because
doesn’t work for tones (ex: fire alarm and not knowing which one is going off without seeing it)
pinna reconstruction can take time how to learn how to localize because the sound would bounce off of it
What is the cocktail party effect?
Ability to attend to or focus one’s attention on a particular stimulus in the presence of other stimuli (target vs. competition or noise)
Define signal to noise ratio (SNR)
the relationship between the desired target (signal) and noise (anything that is not the target)
what is SNR equation
SNR = signal dB level - noise dB level
signal is 40 dB SPL and noise is 45 dB SPL
-5 dB SPL
signal is 40 dB SPL and noise is 40 dB SPL
0 dB SPL
signal is 40 dB SPL and noise is 35 dB SPL
5 dB SPL
What acoustic advantage exists for a person with two ears? What is the term for this?
The “better ear effect”- physically if the target and the noise are separated, there will be one ear with a better SNR.
Having two ears provides the ability to reduce perceptual and acoustic effects of noise
What is binaural squelch?
the auditory systems uses BOTH ears, even the one with the poorer SNR, to provide an advantage in noise.
the ear takes advantage of correlation between the ears to enhance perception
the masking level difference (binaural unmasking)
a mechanism that suppresses echoes due to reverberation
echo suppression
better SNR at ear closer to the signal
better ear advantage
Differentiate between diotic and dichotic presentation of a stimulus.
Diotic = same exact stimulus (in terms of amplitude, frequency, and onset time and phase)
Dichotic= differs in at least one dimension or could even be a different word
Describe the binaural masking level difference experiment. What acoustic cue does the binaural auditory system take advantage of to improve detection of a signal?
ear (using both ears) can reduce the effects of noise to enhance perception of signal (dichotic condition)
In the BMLD experiment, two conditions are compared. In both conditions, a tone is presented in the presence of white noise. In the diotic condition, the tones are in-phase and have the same frequency and amplitude. In the dichotic condition, the tones are 180 degrees out of phase, but have the same frequency and amplitude. This mimics ITD’s and the spatial separation of a tone and noise. Thresholds are BETTER in the dichotic condition.
Describe how the precedence effect and echo suppression account for echoes and reverberations.
The precedence effect says that the sound source localization is based on the first copy of the sound to arrive to the auditory system.
Echo suppression- multiple copies of the sound are suppressed
The auditory system processes one auditory image.
If you had a patient who had a sudden hearing loss in one ear, what perceptual changes might they notice?
trouble localizing
more trouble hearing in noise (loose squelch)
different thresholds (higher)
harder to hear someone’s voice
harder time hearing soft sounds - have a cocktail problem
more trouble in an echo room
threshold of echo suppression is less (binaural system is what suppresses them)
less loudness perception
