Chapter 13: Acoustics & Broadcasting Computation

The noise from an airplane engine 100 m from an observer is found to

have an intensity of 45 dB. What will be the intensity when the plane

flies overhead at an altitude of 1 km?

• A. 23 dB

• B. 25 dB

• C. 27 dB

• D. 29 dB

A sound pressure (RMS) of 125 microbars is equivalent to what sound

pressure level?

• A. 112.92 dB

• B. 113.92 dB

• C. 114.92 dB

• D. 115.92 dB

A car horn outdoors produces a sound intensity level of 90 dB at 10 ft

away. At that distance, what is the sound power in watt?

• A. 0.02 W

• B. 0.04 W

• C. 0.06 W

• D. 0.08 W

In reverberation chamber method, what volume of the chamber is

required if the absorption coefficient is to measure at 500 Hz?

• A. 1.81 m^3

• B. 2.81 m^3

• C. 3.81 m^3

• D. 4.81 m^3

A church has an internal volume of 2550 m3. When it contains 186

metric Sabines of absorption, what will be its reverberation time in

seconds?

• A. 1.1s

• B. 2.2 s

• C. 3.35

• D. 4.4 s

Two sounds of 4 W and 10 W powers are produced at ground level at a

distance of 10 m and 20 m respectively from a listener. If the ground is

level, unobstructed and non-absorbing, what will be the SIL of the

sound heard by the listener?

• A. 90.15 dB

• B. 100.15 dB

• C. 110.15 dB

• D. 120.15 dB

The basic voice band has approximately how many octaves?

• A. 1.32

• B. 2.32

• C. 3.32

• D. 4.32

What is the velocity of sound in dry air when the temperature change is

15 degree Celsius?

• A. 340.6 m/s

• B. 342.6 m/s

• C. 344.6 m/s

• D. 346.6 m/s

For a temperature change of 25 degree Celsius, what is the velocity of

sound in dry air?

• A. 340.3 m/s

• B.342.3 m/s

• C. 344.3 m/s

• D. 346.3 m/s

If the RMS sound pressure is 5 lb/ft2, what is the sound power level?

• A. 5.61 dB

• B. 6.61 dB

• C. 7.61 dB

• D. 8.61 dB