# Audio Engineering MCQ Questions and Answers – Pressure and Intensity of Sound Waves – 2

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This set of Audio Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Pressure and Intensity of Sound Waves – 2”.

1. What is the unit of loudness level for pure tone?
a) Decibel
b) Velocity
c) Phon
d) Wavelength

Explanation: Loudness is frequently expressed in sones. The phon is a unit of loudness level for pure tones. Its purpose is to compensate for the effect of frequency on the perceived loudness of tones. This unit was proposed by S. S. Stevens.

2. What is the newer unit of loudness and is now the international standard?
a) Phon
b) Sone
c) Decibel
d) Frequency

Explanation: Sone is the newer unit of loudness and is now the international standard. Assume the phon as of foot and a sone as a meter. They both measure the same thing, but one is the newer standard. Sone equals to 40 phones. The unit of frequency is Hertz and decibel is the unit of proportion.

3. How much phons is equal to 1 sone?
a) 10
b) 20
c) 30
d) 40

Explanation: 1 sone is equal to the loudness of a 1 KHz tone at a 40 dB sound pressure level. So, 1 sone is equal to 40 phons. Loudness is frequently expressed as sones. Phon is a unit of loudness level for pure tones. Its purpose is to compensate for the effect of frequency on the perceived loudness of tones.

4. What is the full form of SPL?
a) Signal Pressure Level
b) Sound Pressure Level
c) Signal Phase Level
d) Sound Periodic Level

Explanation: Sound pressure level (SPL) is a logarithmic measure of the effective pressure of a sound relative to a reference value. Doubling the sound pressure raises the sound pressure level by 6 dB. Sound pressure levels are measured by a sound level meter called a dB meter.

5. What is called as the sound power per unit area?
a) Sound intensity
b) Sound pressure
c) Sound amplitude
d) Sound velocity

Explanation: “Sound intensity” is sound power per unit area, while ‘pressure’ is a measure of force per unit area. Intensity as a sound energy quantity is not the same as pressure as field quantity. It can be seen that sound intensity may never be equated with “sound pressure”. The sound pressure is the alternating sound pressure as RMS (Root Mean Square) value.

6. Sound pressure is not intensity.
a) True
b) False

Explanation: Sound pressure P is a “sound field quantity” and sound intensity I is a “sound energy quantity”. It can be seen that sound intensity may never be equated with “sound pressure”. So, sound pressure is not intensity.

7. The sound pressure is the alternating sound pressure as RMS value.
a) True
b) False

Explanation: The sound pressure is the alternating sound pressure as RMS value. The sound pressure amplitude is the peak value of the sound pressure. The sound volume is determined mostly by the sound pressure P and expressed as a sound pressure level Lp in dB.

8. Two sounds have levels of 80 dB and 100 dB. What is the difference in sound intensities?
a) 50
b) 100
c) 200
d) 1000

Explanation: L1 = 10 log I1/I0 = 80 dB and
L2 = 10 log I2/I0 = 100 dB
Now Subtracting:
L2 – L1 = 10 (log I1/I0 – log I2/I0)
100 – 80 = 10 log (I2/I1)
20 = 10 log (I2/I1)
2 = log (I2/I1)
I2/I1 = 102
I2 = 100(I1)

Sanfoundry Global Education & Learning Series – Audio Engineering. 