Acoustics and Sound Flashcards

What do equal loudness contours (Fletcher-Munson curves) demonstrate about human hearing?

Answer: The ear's perceived loudness varies with both frequency and sound intensity level

Equal loudness contours show that the human ear's sensitivity is not flat; it is most sensitive around 1,000–4,000 Hz and requires substantially more intensity at very low and very high frequencies to achieve the same perceived loudness.

According to the inverse square law, what happens to sound pressure level when the distance from a point source is doubled?

Answer: It decreases by approximately 6 dB

The inverse square law states that sound intensity decreases as the square of the distance from the source; doubling the distance reduces the SPL by approximately 6 dB in a free field.

Why is acoustic impedance clinically relevant in audiology?

Answer: Impedance mismatches at the middle ear affect energy transfer and are evaluated via tympanometry

Acoustic impedance governs how efficiently sound energy is transferred between structures; tympanometry measures middle ear impedance to identify conditions such as otitis media with effusion or ossicular chain fixation.

What is the fundamental difference between analog and digital signal processing in hearing aids?

Answer: Analog processing is continuous, while digital processing samples the signal and converts it to binary data before processing

Analog processing maintains a continuous electrical representation of the sound wave, whereas digital processing samples the sound at high rates, converts it to binary code, processes it mathematically, then converts it back to an analog output.

What does the 'speech banana' on an audiogram represent?

Answer: The frequency and intensity region (roughly 250–8,000 Hz, 25–65 dB HL) where most conversational speech sounds occur

The speech banana is the banana-shaped region on the audiogram that encompasses the frequencies and intensities of typical spoken language, allowing clinicians to identify which speech sounds a patient cannot hear based on their thresholds.

Which frequency region is most critical for maximizing speech discrimination when fitting hearing aids?

Answer: 2,000–4,000 Hz (high-frequency consonant region)

The 2,000–4,000 Hz region contains high-frequency consonants such as /s/, /sh/, /f/, and /th/, which carry the greatest phonemic information needed for distinguishing words from one another.

What is the occlusion effect in hearing aid acoustics?

Answer: A low-frequency resonance boost of bone-conducted sound perceived when the ear canal is blocked by an earmold or shell

The occlusion effect occurs when an earmold or hearing aid shell occludes the ear canal, trapping and amplifying low-frequency bone-conducted sounds—particularly the wearer's own voice—creating a hollow or 'barrel' voice quality.