IHS Acoustics and Sound 2

Question 1

What does RT60 (reverberation time) measure in room acoustics?

Accepted Answer

The time required for sound to decay by 60 dB after the source stops

Answer

The round-trip travel time of sound between two parallel walls

Answer

The room's frequency response at 60 Hz

Answer

The echo delay measured in milliseconds

Question 2

How does a higher signal-to-noise ratio (SNR) affect speech intelligibility for hearing aid users?

Accepted Answer

It improves speech intelligibility by making the signal stronger relative to background noise

Answer

It reduces speech clarity by masking critical frequencies

Answer

It has no measurable effect on speech understanding

Answer

It increases reverberation in the listening environment

Question 3

What is the primary cause of acoustic feedback in hearing instruments?

Accepted Answer

Amplified sound from the receiver leaking back into the microphone and being re-amplified

Answer

A depleted battery causing voltage fluctuations

Answer

A loose or corroded battery contact

Answer

Excessive cerumen blocking the microphone port

Question 4

What is the key distinction between sound pressure level (SPL) and hearing level (HL)?

Accepted Answer

SPL uses a fixed physical reference (20 µPa); HL is referenced to average normal hearing thresholds that vary by frequency

Answer

SPL is measured in Hz; HL is measured in dB

Answer

SPL is used for hearing aids only; HL is used exclusively for audiometers

Answer

There is no practical difference between the two scales

Question 5

In acoustics, what does one octave represent?

Accepted Answer

A doubling of frequency

Answer

An increase of exactly 1,000 Hz between two tones

Answer

A tenfold increase in sound intensity

Answer

A fixed interval of 8 semitones used only in audiometric testing

Question 6

What is the primary purpose of a directional microphone system in a hearing aid?

Accepted Answer

To improve speech understanding in noise by emphasizing sounds arriving from in front

Answer

To amplify all surrounding sounds equally in every direction

Answer

To eliminate the need for a volume control

Answer

To reduce battery drain compared to omnidirectional microphones

Question 7

What does total harmonic distortion (THD) measure in hearing instrument performance?

Accepted Answer

The ratio of unwanted harmonic energy to the fundamental frequency energy, expressed as a percentage

Answer

The maximum output level of the hearing aid in dB SPL

Answer

The full frequency range of the amplification channels

Answer

The overall gain of the hearing instrument in dB