Sound Design Sound 3 — Questions and Answers
Question 1: In the context of room acoustics, what does RT60 measure?
- The frequency response of a room at 60 Hz
- The time for sound to decay by 60 dB after a source stops (Correct answer)
- The ratio of direct to reflected sound at 60 ms
- The resonant frequency of a 60-square-meter room
Correct answer: The time for sound to decay by 60 dB after a source stops
RT60 (reverberation time) is the duration required for a sound in a room to decrease in intensity by 60 decibels after the sound source ceases.
Question 2: Which acoustic treatment material is most effective at absorbing low-frequency sound energy?
- Thin foam panels
- Acoustic tiles
- Bass traps (Correct answer)
- Diffusers
Correct answer: Bass traps
Bass traps are thick, dense absorptive panels designed specifically to attenuate low-frequency buildup, which thinner materials cannot effectively address.
Question 3: What is a standing wave in a room, and why is it problematic for sound design?
- A wave with no decay, useful for sustain
- A resonant pattern where certain frequencies are boosted or cancelled at fixed positions (Correct answer)
- A wave traveling vertically through the floor
- A very slow sound wave used in subwoofer calibration
Correct answer: A resonant pattern where certain frequencies are boosted or cancelled at fixed positions
Standing waves form when reflected waves interact with incoming waves to create fixed nodes (cancellations) and antinodes (peaks), causing uneven frequency response that varies by listener position.
Question 4: The Haas effect (precedence effect) states that when two identical sounds arrive within roughly 40 ms, the listener:
- Perceives two distinct echoes
- Localizes the source toward the delayed sound
- Fuses them into one sound localized toward the first arrival (Correct answer)
- Experiences phase cancellation
Correct answer: Fuses them into one sound localized toward the first arrival
Within approximately 40 ms, the auditory system fuses early reflections with the direct sound and perceives the combined sound as coming from the direction of the first arrival.
Question 5: Which of the following materials would be LEAST effective as an acoustic absorber?
- Thick curtains
- Carpet
- Concrete walls (Correct answer)
- Fiberglass panels
Correct answer: Concrete walls
Concrete is a hard, dense, non-porous surface that reflects sound rather than absorbing it, making it acoustically reflective.
Question 6: In a recording studio control room, the 'critical distance' refers to:
- The maximum cable run length before signal loss
- The point where direct and reverberant sound fields have equal energy (Correct answer)
- The minimum distance between monitors and the mix position
- The distance at which crosstalk between monitors becomes inaudible
Correct answer: The point where direct and reverberant sound fields have equal energy
Critical distance is the point in a room where the sound energy from direct sound equals the energy from the reverberant field; beyond it, the reverberant field dominates.
Question 7: A diffuser in acoustic treatment works by:
- Absorbing all incoming sound energy
- Scattering reflections in many directions to reduce flutter echo (Correct answer)
- Blocking low frequencies from entering a room
- Increasing the RT60 of a space
Correct answer: Scattering reflections in many directions to reduce flutter echo
Diffusers scatter sound reflections spatially without significantly absorbing energy, breaking up flutter echoes and creating a more even reverberant field.
Sound Design Sound 3
In the context of room acoustics, what does RT60 measure?