acoustic chapters 22, 23, 24

1. The goal of architectural acoustics is as follows:
b) design spaces to meet hearing needs
2. The critical frequency range for human speech communication is:
d) 300 to 4000 Hz
3. Human beings can hear sounds with frequencies ranging from:
b) 20 to 20,000 Hz
4. In architectural acoustics, frequency is sometimes referred to as:
c) sound frequency
5. Which of the following terms does not relate to sound magnitude:
c) sound frequency
6. The decibel is best defined as the following:
a) a numerical scale devised to conveniently describe sound magnitude
. Sound intensity level changes by 3 dB with every doubling or halving of power andchanges by ____ dB with every doubling or halving of the distance from a pointsource.

6
8. A typical sound pressure level (dBA) for human breathing is 10, and for a jet planetakeoff is 150. The threshold of discomfort is about ____ dBA
110
9. The following is not a definition of noise:
d) sound outside of the normative frequency ranges
10.

Which of the following is not a correct conclusion regarding annoyance as a result ofnoise. Annoyance is:

d) greater for nonsense noise (foreign language) than information-bearingnoise (a neighbor’s radio)
11. Prolonged exposure to high noise levels can lead to hearing loss. Which of thefollowing US-based agencies publishes acceptable noise exposure limits for workers.
OSHA
The Articulation Index (AI) is determined by reading a carefully selected set ofphonetically balanced nonsense syllables to a test audience in the presence ofdifferent levels of background noise. An AI (ratio of correctly identified syllables tototal syllables) of ____ is usually deemed an acceptable level of intelligibility for amale voice.
0.

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5

A. A tone with a sound pressure level of 84 dB at 100 Hz frequency would soundequally as loud as a tone of:___ db at 40 Hz 97___ dB at 200 Hz 79___ dB at 1000 Hz 80___ dB at 2000 Hz 77___ dB at 4000 Hz 70
_97__ db at 40 Hz79_ dB at 200 Hz 79_80__ dB at 1000 Hz__77_ dB at 2000 Hz70 dB at 4000 Hz
B. What is the combined sound pressure level for the following situations:40 dB + 40 dB 43 dB52 dB + 50 dB 54 dB52 dB + 58 dB 59 dB55 dB + 40 dB 55 dB
40 dB + 40 dB _43 dB_52 dB + 50 dB _54 dB_52 dB + 58 dB _59 dB_55 dB + 40 dB _55 dB_
1. The two primary acoustical characteristics of an enclosed space are:
d) absorption and reverberation
2. The term used to define a material’s sound absorption characteristic is:
b) coefficient of absorption
3. Reverberation is the persistence of sound after a sound source has ceased. Suchpersistence of sound is a result of:
b) repeated reflections
4.

Reverberation time (TR) is defined as the time required for the sound pressure levelto decrease ____ dB after the sound source has stopped producing sound.

60
5. The converse of reverberation is articulation.

An articulate environment keeps eachsound event separate rather than running them together. Spaces for speechactivities should be:

b) more articulate, less reverberant
6. Most indoor spaces contain the following sound fields:
c) a near field, a reverberant field, and a free field
7. Sound power level (PWL) is a measure of the amount of sound generated by asource _____ of its environment.
d) independent
8. The noise reduction coefficient (NRC) is:
a) an arithmetic average of absorption coefficients at four frequencies
9. The optimum reverberation time in seconds, for speech, can be approximated usinga formula based on the _____ of the space.

c) spatial volume
10. Concave domes, vaults, or walls will lead reflected sound into certain areas of aroom. This is called:
a) focusing
11. _______ is a design procedure for analyzing the reflected sound distributionthroughout a hall using the first reflection only.
c) Ray diagramming
12. Generally, sound amplification systems will be required in spaces larger than ____ft2 (m2).
c) 50,000 (4645)
1. The process of converting acoustical energy into heat is called:
d) sound absorption
2.

Absorption techniques are generally useful and effective:

b) to change room reverberation characteristics
3. Structure-borne sound transmission is generally ______ than airborne sound.
c) more difficult to control
4. The noise reduction (NR) between two spaces separated by a barrier is defined as:
b) the difference between the sound intensity levels in the two rooms
5. The mass law is based on the principle that:
a) the larger the mass, the less it will vibrate
6. Stiffness in a panel construction reduces damping, making it a good ______
b) transmitter
7. The stiffness of a barrier is a function of its ______ and the rigidity of its mounting.

c) material composition
8. Transmission loss for a cavity wall increases with the width of the air space at therate of 5 dB per doubling. Performance can be improved still further by:
d) filling the void with porous, sound-absorbent material
9. ______ is a function of the degree of sound isolation provided by the barriersbetween rooms and the ambient sound level in the receiving room.
b) speech privacy
10. An AI (Articulation Index) of 0 indicates:
c) ideal speech privacy
11.

Which of the following is not a reason that impact noise is at least as serious aproblem as airborne noise:

a) resilient cushioning materials eliminate vibration
12. Which of the following is not a form of isolation for structure-borne sound.
b) reducing mechanical equipment sound power