Midterm Review Flashcards
What is the difference between custom, modular and semi-modular hearing aids?
Custom hearing aids are customized to the specifics of a patient’s ear. Hearing aid components are manufactured to work and fit within a custom shell based on a patient’s ear impression.
Modular hearing aids consist of standardized components that come in a variety of sizes but are not customized to the patient’s ear. They can be faster to obtain, cheaper, and possibly disposable.
Semi-modular hearing aids may tailor the shell, but the inner components are typically standardized.
What steps can be taken to improve hearing aid reliability?
Covering the mic – water/sweat resistant
Nanocoating, waterproofing, water repellent layers to keep moisture out
Automatic volume controls, swipe controls
Electrical programming
How does a CROS (contralateral routing of the signal) hearing aid function?
There are two devices, one in a profoundly deaf ear and one in a good ear; it
transfers the signal from the better ear to the worse ear. This is good for a unilateral
hearing loss if there is one unaidable ear.
What are the components needed for hearing aid programming?
A computer (and something to connect the hearing aid to the computer)
Hardware to connect HA to computer (e.g. HiPro)
Software to program the connected HA (e.g. NOAH, manufacturer software)
What is reverberation? How do you eliminate the ill-effects of reverberation on speech perception?
Delayed versions of the sound from the original sound; the sound is smeared out in
time and less audible
To prevent reverberation:
Carpeting/Curtains
Don’t use an empty room
Acoustically treated walls
Take sound where it is the strongest (e.g. right by the speaker’s mouth) and
transmit it directly into the listener’s ear. [wireless transmission]
Compare induction loop vs FM vs IR vs sound amplification system.
Induction loop:
Sound is converted to an electric current that travels through wires around a
room. Can be transmitted to a hearing aid/device via electromagnetic waves. Is not ideal for privacy, can be picked up in adjacent rooms. Signal can be affected by where someone sits in a room
Frequency Modulation (FM) System:
Talker wears a microphone and hearing-impaired person wears receiver. More portable system. Signal is not converted into another form of energy but rather modulates.
Infrared (IR) transmission
Audio signals transferred via infrared electromagnetic waves. Similar to radio signals but occurs at very high frequencies. Because at same frequency of light waves, easily blocked by opaque things. Cannot be used in direct sunlight. Used in closed spaces / short distances. Good for places that need privacy (ex. Courtrooms)
Sound amplification
A PA system, contains a microphone and a loudspeaker. Relatively easiest to set up. Gives clear feedback to the speaker when there is an issue. Improves the SNR for all listeners in a room, but not to the same degree of benefit you’d see with the other systems. Can still be prone to reverb.
What is SSPL?
Saturated Sound Pressure Level. Measure of maximum output of a hearing aid.
What are different types of real ear measurements?
Real ear to coupler difference (RECD)
Real ear insertion gain (REIG) - first you do aided gain, with the HA on the ear in
position, then you do a second measurement without the HA.
Real ear unaided gain (REUG) -measures the resonance and natural gain of the
canal without amplification and occlusion
Real ear occluded gain (REOG) -measures the gain in signal level when the canal is
occluded with the coupler but not amplified
What are the differences between electroacoustic measurements and real ear
measurements.
Electroacoustic measures are for quality control – not done on the patient. Use couplers instead of the patient’s ear – gives an approximation but not exact because every ear is different. Some performed at full on gain (don’t do on a patient because you would just blow their hearing and it would be painful). Want to make sure the HA is calibrated according the ANSI and the manufacturer’s standards
Real ear measurements are done on the patient. Provides information about the actual dB levels reaching the patient’s ear to determine whether desired levels are being obtained.
What are the different couplers used in hearing aid measurements? Which hearing aid styles are they compatible with?
HA1 coupler: used for ITE and ITC aids; does not include ear mold simulator
HA2 coupler: used for pocket or body hearing aids; includes an earmold simulator
(which is connected to the BTE hearing aid tubing or the receiver of body aid)
HA4: variation of HA2 coupler used for BTE or spectacle aids and is rarely used
Explain gain frequency response vs. OSPL90
GFR:
Measure output when input is 50 or 60dB. American standard is 50dB, and you test to see the gain at all frequencies. Measured with full on gain setting, trying to match up our results with the manufacturer targets at a semi-loud level and not at an extreme loudness like 90 dB.
OSPL90:
90dB SPL is the max input that a HA can handle. Output you get out of the hearing aid when an input of 90 dB SPL is presented. Measured with full on gain setting.
Explain Input Output Functions
Examine the gains / outputs at each frequency across a range of SPLs
that are inputted (go from softer to louder sounds)
You want to show a non-linear graph for a non linear hearing aid»_space;
showcases compression to avoid peak clipping and distortion
Compression threshold = level where the curve / graph changes from
linear to compression
Explain Distortion
Artifacts or extraneous signals that interfere with the main signal
If >10%, not good for speech perception
A common type of distortion is harmonic distortion, where harmonics
in a complex sound interfere with the listener hearing that sound
Is measured to ensure that:
▪ Hearing aids meet their required specifications
▪ Compare the sound quality of two hearing aids
▪ Determine the maximum output of hearing aid before a signal
is clipped/distorted
Explain a Magnetic Response
See the strength of the telecoil (on RTG position)
Measured with HA in test box
Compare against manufacturer’s standards
Explain the real ear to coupler difference
Acoustics in a 2cc coupler are different than the acoustics in the ear, and each ear is
different. There will always be a gap between electroacoustic and real ear measurements because the coupler will never mimic a real person’s ear canal + middle ear. A negative RECD = inadequate seal of the transducer to the ear (e.g., foam ear tip), a larger than average ear, or a poorly placed probe tip. Useful in HA fitting and audiometry, esp. with babies or people with small ECs
