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Flashcards in Acoustics Deck (120)
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1

Reverberation Time? Units?

T; sec

2

Transmission loss

TL; dB

3

What is the articulation index?

a measure of speech intelligibility calculated from the number of words read from a selected list that are understood by an audience. A low articulation index (less than 0.15) is desireable for speech privacy whereas a high articulation index (above 0.6) is desried for good communication

4

What is attenuation?

The reduction of sound

5

What is amplificiation?

The increased intensity of sound by mechanical or electrical means

6

What is frequency?

The number of pressure fluctuations or cycles occurring in 1 sec, expressed in Hz

7

What is a Hertz?

The unit of frequency; 1 cycle per second equals 1 Hz

8

What is Impact insulation class (IIC)?

A single number rating of a floor ceiling’s impact sound transmission performance at various frequencies

9

What it Noise criteria (NC)?

A set of single number ratings of acceptable background noise corresponding to a set of curves specifying sound pressure levels across octave bands. Noise criteria curves can be used to specify continuous background noise, achivesound isolation and evaluate existing noise situations

10

What is Noise Insulation class (NIC)`?

A single number rating of noise reduction

11

What is Noise Reduction (NR)?

The arithmetic difference, in decibels, between the intensity levels in two rooms separated by a barrier of a given transmission loss. Noise reduction is dependent on the transmission loss of the barrier, and the absorption of the surfaces of the receiving room.

12

What is the Noise reduction coeeficient(NRC)?

The average sound absorption coefficient to the nearest 0.05, measured at the four one-third octave band center frequencies of 250, 500, 1000, and 2000 Hz

13

What is Reverberation?

The persistence of a sound in a room after the source has stopped producing sound

14

What is a Octave band?

A range of frequencies in which the upper frequency is twice that of the lower

15

What is a phon?

A unit of loudness level of a sound equaltot he sound pressure level of a 1000 Hz tone judged to be as loud

16

What is Sound transmission class (STC)?

A single number average over several frequency bands of a barriers ability to reduce sound. The higher the STC rating, the better the barrier’s ability to control transmission

17

What is Transmisison Loss (TL)?

The difference, in decibels, between the sound power incident on a barrier in a source room and the sound power radiated into a receiving room on the opposite side of the barrier. The transmission loss varies with the frequency being tested

18

What are the 3 basic qualities of sound?

Velocity, frequency, and power

19

What is the velocity of sound in air?

1130 ft/sec

20

At what absorption coefficient is a material considered absorbing?

Above 0.2

21

What is the equation for acoustical absorption (A)?

A=Sa

22

What should the average absorption coefficient be for a room?

.20

23

Are higher or lower absorption coefficient suitable for large rooms?

Lower

24

What effect does each doubling of the amount of absorption have on a room?

3dB difference

25

If additional absorptive material is being added to a room, the total absorptions should be increased by how much to be noticeable?

3 times

26

Each doubling of the absorption in a room reduces reverberation by how much?

One-half

27

Where are absorptive materials more effective when placed in large rooms?

Ceiling

28

Where are absorptive materials more effective when placed in small rooms?

Walls

29

Generally absorption increase with an increase in what of a poruous absorber?

Thickness

30

The amount of absorption of a porous type of sound absorber such as fiberglass or mineral wool is dependent on what 4 factors?

1) thickness; 2) density; 3)porosity; 4) orientation of fibers in material should be composed of open, interconnected voids