Acoustics and Sound Flashcards

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

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

RT60 is the time required for sound energy to decay by 60 dB after the source stops, serving as the standard metric for room reverberation and its impact on speech clarity.

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

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

A higher SNR means the desired speech signal is substantially louder than background noise, directly improving the listener's ability to understand speech, especially for those with hearing loss.

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

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

Acoustic feedback is a closed loop where amplified sound from the receiver (speaker) escapes and re-enters the microphone, is amplified again, and creates the characteristic whistle or squeal.

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

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

SPL is referenced to a fixed pressure of 20 µPa across all frequencies, while HL adjusts for the ear's varying sensitivity so that 0 dB HL represents the average normal hearing threshold at each test frequency.

In acoustics, what does one octave represent?

Answer: A doubling of frequency

One octave equals a doubling of frequency; for example, 500 Hz to 1,000 Hz is one octave, and 1,000 Hz to 2,000 Hz is the next octave.

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

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

Directional microphones enhance sounds arriving from in front while attenuating sounds from behind and the sides, effectively improving the signal-to-noise ratio during face-to-face communication.

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

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

THD quantifies the distortion introduced by a hearing aid by measuring energy in harmonic frequencies relative to the intended fundamental, with lower percentages indicating cleaner, higher-quality amplification.