Hearing Aids Final Exam

The range between the softest and loudest sounds a person can hear comfortably.

What is dynamic range (DR)?

SNHL reduces dynamic range, often due to recruitment.

How does hearing loss affect dynamic range?

A method to fit a wide range of input levels into the reduced dynamic range of someone with hearing loss using automatic gain adjustments.

What is Wide Dynamic Range Compressions (WDRC)?

Linear gives the same gain regardless of input level; compression reduces gain as input increases.

What is the main difference between linear and compression amplification?

The input level where compression begins— below it, gain is linear; above it, gain is reduced

What is a compression kneepoint (CK or TK)?

For patients with recruitment (common in SNHL)

When is a low TK beneficial?

For conductive HL or experienced hearing aid users

When is a high TK beneficial?

The change in input required to achieve a 1 dB change in output.

Ex: 2:1 means 2 dB input change gives 1 dB output change.

What is the compression ratio (CR)?

1:1

What CR is considered linear?

1.5:1 to 3:1

What are typical CRs for WDRC?

To make soft sounds audible and loud sounds comfortable by mimicking cochlear compression.

What is the role of compression in hearing aids?

An outdated method that cuts off signal peaks when too loud, causing distortion.

What is peak clipping?

It limits output without causing distortion.

Why is compression better than peak clipping?

A system where gain adjusts automatically based on input level

What is AGC (Automatic Gain Control)?

AGC-I

• input controlled

• volume after compression

AGC-O

• output controlled

• volume before compression

Difference between AGC-I and AGC-O?

The time it takes for compression to begin after input exceeds the kneepoint.

What is attack time?

Time it takes for compression to stop once input falls below kneepoint.

What is release time?

Short attack/release times; good for speech clarity but may cause pumping.

What is fast-acting compression (syllabic/phonemic)?

Longer attack/release time; smoother sound but can miss sudden changes in input

What is slow-acting compression (AVC/SAVC)?

Different CRs and kneepoints for different frequency bands.

What is multichannel compression?

It can smear intensity differences between speech sounds and reduce clarity.

Why might too many channels be bad?

Opposite of compression; reduces low-level sounds below the kneepoint

What is expansion?

• Avoids discomfort

• Improves clarity

• Normalizes loudness

• Increases comfort and intelligibility

What are some benefits of compression?

• WDRC

• Output limiting

• Syllabic (fast acting)

• Slow acting

• Adaptive/dual compression

What are some types of compression?

The patient kept her TV too loud, so the HA reduced gain via compression. Problem resolved after lowering TV volume.

What was the case study about “The Lady and the TV”?

They may be misleading—clinicians should interpret fitting ranges critically.

What is the danger of relying on manufacturer spec sheets?

Manufacturer’s default for new users; usually prioritize comfort with high compression.

What are “first fit” settings?

They may oversimplify and unintentionally alter compression too much.

Why should fitting wizards be used cautiously?

Turn on expansion

What’s a common solution if a patient says “HA sounds too noisy”?

Keep below 3:1; for music, closer to 1:1 is ideal

Rule of thumb for CRs?

• Background noise level

• Distance from the sound source

• Room acoustics

Name three environmental factors that affect SNR.

It reduces the ability to separate speech from noise, increases difficulty in complex environments, and creates central processing challenges.

How does hearing loss impact SNR?

Directional microphones and remote microphone.

What are two types of microphones that improve SNR in hearing aids?

To measure SNR loss

What is the purpose of the QuickSIN test?

Electroacoustic analysis.

It is recommended by ASHA, AAA and APSI for all new and repaired hearing aids as part of standard adult and pediatric practice.

What is EAA and when is it recommended?

ANSI: American National Standards Institute

IEC: International Electrotechnical Institute

FOG: Full on gain

RTG: Reference test gain

OSPL90: Output sound pressure level for a 90 dB input

Define these terms: ANSI, IEC, FOG, RTG, OSPL90

The OSPL90 curve shows coupler SPL as a function of frequency for a 90 dB input.

• Max OSPL90 is the maximum value of the curve.

• Avg OSPL90 is the average at high-frequency average (HFA): 1000, 16000, 2500 Hz

• SPA refers to special purpose average selected by the manufacurer.

What does the OSPL90 curve represent, and how is Max OSPL90 calculated?

Avg FOG is the average gain at HFA frequencies with a 50 dB input.

How is average FOG measured?

• RTG measures gain at HFA using a 60 dB input

• Frequency range is defined as the lowest to highest frequencies where the response curve is within 20 dB of the HFA gain.

What does RTG measure and how is frequency range defined?

500, 800, and 1600 Hz, comparing the power of the harmonic to the fundamental

At what frequencies is harmonic distortion assessed?

• Frequency response

• Gain

• Distortion

• Output

• Input/output characteristics

Name the 5 parameters assessed in EAA.

• Volume too large for typical ear canals

• Impedance and standing waves not accurately represented

• Earmold “plumbing” differences not captured

• Do not mimic real-ear acoustic environment

Why are 2cc couplers not always ideal for hearing aid verification?

They simulate acoustic properties of the human ear more accurately than couplers and are used for more realistic verification.

What is the purpose of real ear simulators in hearing aid testing?

• KEMAR: Manakin that simulates head and torso; used for REM without human subjects.

• CARL: Used for clinical training and research in hearing aid verification.

What is KEMAR and how is it different from CARL?

It was an early real ear simulator developed in the 1960s but is no longer manufactured.

What is the Zwislocki coupler and is it still used?

Color, style, processor, volume control, battery door, tamper resistance, directional microphones, t-coil, receiver, and charger

What are some components to check during prefitting quality assessment of a new hearing aid (HA)?

To ensure the HA meets specifications, works properly, and provides a quality benchmark for future checks.

Why is it important to test the electronics of a hearing aid before fitting?

ANSI S3.22 (2009) outlines specifications for hearing aid characteristics including measurement methods and tolerances.

What is ANSI S3.22 and what does it cover?

HA-1 is used for ITE, ITC, CIC, RIC

HA-2 includes earmold simulator and is used for BTEs

What’s the difference between HA-1 and HA-2 couplers?

Open fits require special seals or methods to avoid leakage and user error; incorrect setup can skew results.

Why is using the correct coupler setup important for open-fit HAs?

Full calibration every 2 years; Quick check weekly/daily depending on protocol

How often should test boxes be calibrated?