IHS Acoustics and Sound 1 — Questions and Answers
Question 1: What is the standard unit used to measure sound frequency?
- Decibel (dB)
- Hertz (Hz) (Correct answer)
- Pascal (Pa)
- Watt (W)
Correct answer: Hertz (Hz)
Hertz (Hz) measures the number of complete sound wave cycles per second and is the universally accepted unit for sound frequency.
Question 2: Compared to a 0 dB SPL reference, a 20 dB SPL sound is how many times more intense?
- 2 times
- 10 times
- 100 times (Correct answer)
- 1,000 times
Correct answer: 100 times
The decibel scale is logarithmic; each 10 dB increase represents a tenfold increase in intensity, so 20 dB equals 100 times the intensity of the reference level.
Question 3: Which frequency range is most critical for speech intelligibility?
- 125–500 Hz
- 500–4,000 Hz (Correct answer)
- 4,000–8,000 Hz
- 8,000–12,000 Hz
Correct answer: 500–4,000 Hz
The 500–4,000 Hz range contains the most important frequencies for speech intelligibility, encompassing the primary energy of most vowels and consonants.
Question 4: Approximately how fast does sound travel through air at 20°C (68°F)?
- 343 meters per second (Correct answer)
- 760 meters per second
- 1,125 meters per second
- 1,500 meters per second
Correct answer: 343 meters per second
Sound travels at approximately 343 meters per second (about 1,125 feet per second) through air under standard room-temperature conditions.
Question 5: Which of the following best describes a pure tone?
- A broadband noise signal spanning all frequencies
- A complex waveform with multiple harmonics
- A single-frequency sinusoidal sound wave (Correct answer)
- A tone consisting of two simultaneous frequencies
Correct answer: A single-frequency sinusoidal sound wave
A pure tone is a single-frequency, sinusoidal sound wave with no harmonics or overtones, analogous to the sound produced by a tuning fork.
Question 6: What is the mathematical relationship between the frequency and wavelength of a sound wave?
- Directly proportional
- Inversely proportional (Correct answer)
- Exponentially proportional
- Independent of each other
Correct answer: Inversely proportional
Frequency and wavelength are inversely proportional; as frequency increases, wavelength decreases, governed by the formula: wavelength = speed of sound ÷ frequency.
Question 7: What is the commonly cited threshold of pain for sound pressure level in humans?
- 85 dB SPL
- 100 dB SPL
- 120 dB SPL
- 140 dB SPL (Correct answer)
Correct answer: 140 dB SPL
The threshold of pain is approximately 140 dB SPL, the level at which sound causes immediate discomfort or pain and can result in acute hearing damage.
IHS Acoustics and Sound 1
What is the standard unit used to measure sound frequency?