CAOHC - Council for Accreditation in Occupational Hearing Conservation Physics of Sound and Anatomy 1 โ Questions and Answers
Question 1: The decibel (dB) scale used to measure sound intensity is best described as:
- A linear scale where each unit represents an equal increase in energy
- A logarithmic scale based on ratios relative to a reference pressure (Correct answer)
- An exponential scale based on absolute sound pressure in Pascals
- A linear scale derived from the speed of sound in air
Correct answer: A logarithmic scale based on ratios relative to a reference pressure
The decibel scale is logarithmic, meaning each 10 dB increase represents a tenfold increase in intensity. It expresses sound levels as ratios relative to a reference pressure (20 ยตPa for airborne sound), which mirrors how the human ear perceives loudness differences.
Question 2: What is the primary role of the tympanic membrane (eardrum) in the hearing process?
- It filters high-frequency sounds before they enter the cochlea
- It converts airborne sound pressure waves into mechanical vibrations (Correct answer)
- It equalizes pressure between the middle and outer ear
- It amplifies low-frequency sounds through resonance
Correct answer: It converts airborne sound pressure waves into mechanical vibrations
The tympanic membrane vibrates in response to incoming sound pressure waves, converting acoustic energy into mechanical motion that is then transmitted to the ossicular chain. This transduction step bridges the outer and middle ear.
Question 3: The Eustachian tube connects the middle ear to the:
- Inner ear vestibule
- External auditory canal
- Nasopharynx (Correct answer)
- Cochlear aqueduct
Correct answer: Nasopharynx
The Eustachian tube links the middle ear cavity to the nasopharynx, allowing pressure equalization between the middle ear and ambient atmospheric pressure. Dysfunction can impair ossicular movement and reduce hearing sensitivity.
Question 4: If the frequency of a sound wave doubles, what happens to its wavelength (assuming the speed of sound remains constant)?
- The wavelength doubles
- The wavelength is halved (Correct answer)
- The wavelength remains unchanged
- The wavelength increases fourfold
Correct answer: The wavelength is halved
Wavelength, frequency, and the speed of sound are related by the formula: speed = frequency ร wavelength. Since the speed of sound in air is constant (~344 m/s), doubling the frequency requires the wavelength to be halved to maintain the equation.
Question 5: Along the basilar membrane within the cochlea, where are high-frequency sounds preferentially detected?
- At the apex (helicotrema end)
- At the base near the oval window (Correct answer)
- In the middle section called the scala media
- Uniformly distributed along the entire length
Correct answer: At the base near the oval window
The basilar membrane is tonotopically organized. High frequencies cause maximum displacement near the base (stiff, narrow region near the oval window), while low frequencies cause maximum displacement near the apex (flexible, wider region). This spatial mapping is fundamental to frequency discrimination.
Question 6: What term describes the number of complete cycles a sound wave completes per second?
- Amplitude
- Intensity
- Frequency (Correct answer)
- Phase
Correct answer: Frequency
Frequency, measured in Hertz (Hz), is defined as the number of complete wave cycles occurring per second. Frequency determines the pitch of a sound โ higher frequency corresponds to a higher perceived pitch. It is distinct from amplitude, which relates to loudness.
CAOHC - Council for Accreditation in Occupational Hearing Conservation Physics of Sound and Anatomy 1
The decibel (dB) scale used to measure sound intensity is best described as: