Exam 1 Flashcards
Week 1-4
What is a unit of measurement for sound pressure, intensity or power:
Decibel
What is the name for a Lisener’s perception of the frequency of a pure tone?
Pitch
What is the name for the fraction of an incident sound that bounces off a material?
Reflectance
What is the name for the fraction of an incident sound that is turned into heat within a material?
Absorption
A 10 dB increase represents a perceived loudness increase of:
Twice as much
Reverberation times for small to medium spaces designed to facilitate speech should fall between:
0.4 – 0.8 seconds
The physical principle underlying free-field sound propagation is:
The Inverse Square Law
The minimum threshold of human hearing occurs at 0 decibels.
True or False ?
True
What is reverberation defined as?
A persistence of sound in a space after the sound source has stopped
what is sound converted into in the process known as sound absorption?
Heat
What does Reverberation Time measure?
The time it takes for a sound to drop 60 dB
NRC is a good indication of a material’s ability to absorb sound at all frequencies.
True or False
False
A material with a NRC of 0.10 is more absorbent than one rated at 0.75.
True or False
False
STC is a single number rating that expresses:
The transmission loss of a material or construction assembly
“Flanking” describes the ability of sound to:
Find the path of least resistance
There is more diffraction with low frequency sounds than with high.
True or False
True
In auditorium spaces, seat upholstery and audience members significantly contribute to the sound absorption of the space.
True or False
True
What is the name for a sound that is reflected between parallel surfaces of a space?
Flutter Echo
Which of the following is desirable for music performances as it spreads the sound evenly over a wide seating area?
Diffusion
An interior designer would like to specify a new porous material for a manufacturing space but it must
absorb sound from a machine that produces low frequency. As a professional she should do which of
the following?
Check the material’s absorption coefficient for the particular frequency that the machine emits
What are the three common elements in acoustic systems?
Source (made louder or softer) , transmission path (transmit more or less sound), and receiver (condition and ability for the listener to receive sound)
The human ear’s response to pressure fluctuations in the air caused by:
Vibrating Objects and Air Turbulence which are both sound sources
What is a wave?
A wave is a disturbance or variation that transfers energy from point to point in a medium.
What is frequency?
Frequency is the speed of the oscillations, the time taken for one compression / decompression cycle.
Frequency is measured in cycles per second
Sound Waves – Stationary Source
Sound energy waves can be pictured radiating in air as a series of concentric rings or spheres growing in size
Sound Waves – Moving Source
The wavefronts are produced with the same frequency as before. However, since the source is moving, the center of each new wavefront is now slightly displaced to the right.
How will an observer in front of a moving source hear the source in comparison to an observer behind the source?
An observer in front of the source will hear a higher frequency and an observer behind the source will hear a lower frequency
What is the speed of sound in air at sea level?
About 340 m/s or about 750 mph
- an observer in front of the source will detect nothing until the source arrives