Acoustics and Sound Flashcards

Which type of microphone converts sound pressure variations into electrical signals through the movement of a coil within a magnetic field?

Answer: Dynamic (moving-coil) microphone

A dynamic microphone uses electromagnetic induction: a diaphragm attached to a coil moves within a magnetic field, generating a voltage.

The critical band concept in psychoacoustics refers to:

Answer: A frequency range within which two tones interact and mask each other

A critical band is a frequency region of the cochlear basilar membrane within which stimuli interact, causing masking and affecting loudness perception.

Harmonic distortion in a hearing aid occurs when the device produces:

Answer: Output frequencies that are integer multiples of the input frequency

Harmonic distortion adds overtones at whole-number multiples (harmonics) of the input frequency, degrading sound quality.

Reverberation time (RT60) is defined as the time required for sound pressure level to decrease by:

Answer: 60 dB after the source stops

RT60 is the time it takes for the sound energy in a room to decay by 60 dB once the sound source ceases.

What term describes the frequency at which a structure naturally vibrates when excited, with minimal energy input?

Answer: Resonant frequency

The resonant frequency is the natural vibration frequency of a structure; at this frequency, even small driving forces produce large oscillations.

Which measure represents the ratio of the sound power output of a device to the electrical power input, expressed as a percentage?

Answer: Electroacoustic efficiency

Electroacoustic efficiency expresses how effectively a transducer (e.g., hearing aid receiver) converts electrical energy into acoustic energy.

In audiometric testing, 'insert earphones' reduce the chance of collapsed ear canals and also provide greater attenuation of contralateral sound. Their typical inter-aural attenuation is approximately:

Answer: 70–80 dB

Insert earphones provide approximately 70–80 dB of inter-aural attenuation, substantially more than supra-aural earphones (~40 dB), reducing the need for masking.