First Year Exam: Hearing Aids

What is expansion acoustically?

The decrease in output is greater than the decrease in input

What is the purpose of expansion?

allows the hearing aid to amplify soft speech without overamplifying low-level ambient noise and microphone noise

What does expansion mean for the patient?

This means that the patient's hearing aid will reduce very soft sounds that the patient does not need to listen to, such as ambient noises or the microphone noise of the hearing aids. This provides a more comfortable listening environment in quiet for the patient without needing to make as many manual adjustments on the hearing aids to tune out the very soft speech.

Expansion is best used for patients who have

good low-frequency hearing (normal to mild-to-moderate)

What is the expansion threshold?

the lowest input level at which expansion will be triggered, and hearing aid gain will be reduced for very soft sounds

What is a low threshold kneepoint?

< or equal to 45 dB SPL that allows for more gain for soft speech, but also increases hearing aid noise

What is a high threshold kneepoint?

> 45 dB SPL input, which makes for a quieter hearing aid but also makes speech harder to hear

When expansion is triggered by a decrease in level below the expansion threshold, when this happens, there is a

attack time

When the level rises above the expansion threshold,

there is a release from expansion

While expansion can reduce low-level noise, it does not improve

speech intelligibility

What is attack time?

the time it takes for gain to stablize following an abrupt decrease in input level below TK

What is release time?

The time it takes for the gain to stabilize following an abrupt increase in input level above TK

What will fast attack time do?

will the limit the amplification of ambient sounds, but will also make the hearing aid more likely to go into expansion during pauses in speech

What is the slow-release time?

will make the hearing aid slow to recover when the input level increases, making parts of speech inaudible

Which one is advocated?

a slow attack with fast release to make weak environmental and hearing aid sounds inaudible, with little effect on speech audibility

The direction of input for the mechanism to be triggered is

below TK

What happens to the speech-mapping and I/O functions for expansion?

What is the purpose of the wide dynamic range compression (WRDC)?

It helps maintain audibility for soft speech and comfort for loud sounds, and optimizes a limited dynamic range

Why does WRDC optimize a limited dynamic range?

Provides high gain for low input levels, making more of the speech signal audible, and reduces gain for high inputs. WRDC can help avoid loudness discomfort.

How does WRDC work acoustically?

The gain that is applied to the signal is inversely proportional to the input level, so when the input level goes up, the gain decreases, but when the input level goes down, the gain goes up

What does WDRC mean for the patient?

For the patient it will allow soft sounds to be amplified enough to be heard while keeping loud sounds comfortable. It will improve their speech intelligibility and increase comfort

What happens to the speech map, I/O functions for WDRC?

Who are considered candidates for WDRC?

Patients with a hearing loss no worse than moderate-severe because there is not enough residual dynamic range for WDRC to provide the necessary high gain for moderately loud sounds

What is the threshold kneepoint?

Around 50 and 2 dB increase in input = 1 dB increase in output

What is the direction of input for the mechanism to be triggered?

above TK

What is output limiting compression (OLC) acoustically?

Rapidly turns down the gain once output levels get near the LDL or OSPL90 (whichever is lower)

What is the purpose of output limiting compression?

to limit maximum power output (MPO) so keep hearing aid output from exceeding the LDL fo the hearing aid user and avoids distortion or further damage to the ear

What is the fitting range for a regular ITE (full shell) HA?

normal to moderately-severe

What is the fitting range for a power ITE (full shell)?

mild to profound

What is the fitting range for a regular ITC (half shell)?

normal to moderately-severe and severe in HF

What is the fitting range for a power ITC (half shell)?

mild to severe, profound in HF

What is the fitting range for a regular CIC?

normal to moderately severe, but severe in HF

What is the fitting range for a power CIC?

mild to severe, but profound in HF

What is an ITE?

fills the concha bowl and is more visible

-since it is larger, there is more room for components

-used for mild to severe losses

What is an ITC?

- good for cosmetics, but can be difficult to remove

-small in size, so may not be able to hold all components

-need to have good dexterity to handle and change the battery

-limits the receiver size to be milder to moderate-to-severe hearing loss

What is a CIC?

fits completely in the canal which makes it nearly invisible, which makes it hard to adjust or remove, dexterity is more of an issue

What is the first disadvantage of a CIC?

-limited gain/output for moderate or more severe hearing losses

What is the second disadvantage of a CIC?

more prone to feedback because the mic is near the slit leaks

What is the third disadvantage of a CIC?

cannot put directional mics in them

What is the fourth disadvantage of a CIC?

no room for volume or programming controls

What is the fifth disadvantage of a CIC?

requires more frequent repairs due to moisture or cerumen

What is a conventional and power BTE?

-output of sound is generated by the receiver in the case and is transmitted to the ear canal by tubing which is terminated by an EM

-mild to profound HL

What is a miniBTE?

-can be nearly invisible

-receiver size is limited by the size of the case, so it cannot be used for more severe hearing losses

-wont be able to have certain features

What are some advantages of BTE over custom?

-better durability

-easier to see and feel the controls and better battery compartment

-stronger telecoil

-ability to have direct audio input

-larger, longer battery life

-potential for same day fittings

What is the fitting range for a power BTE?

mild to profound

What is the fitting range for a super power BTE?

moderate to profound

When would an occlusion effect be an issue?

Occlusion is most problematic in patients with near-normal low-frequency thresholds.

Why would we choose an Oticon Zeal?

It is rechargeable, has Bluetooth capabilities, and would be AI-powered to analyze sound environments in real time. For instance, if Kate were in a noisy environment, the hearing aid would take note of that and prioritize speech sounds and reduce the background noise to make it easier for her to understand conversations.