This set of Building Construction Multiple Choice Questions & Answers (MCQs) focuses on “Acoustics – Characteristics of Audible Sound”.
1. Which of the following is not a characteristic of sound?
Explanation: There are three characteristics of sound. These are intensity and loudness, frequency and pitch, and quality or timbre.
2. Sound travels faster in gases than in solids.
Explanation: A sound wave is a longitudinal wave. Sound is transmitted in the form of these longitudinal waves which are a series of compressions and rarefactions created in the medium through which the sound propagates. The velocity of the sound depends on the medium through which it travels. Sound travels faster in solids than in gases.
3. The velocity of sound in bricks is ______
a) 1450 m/sec
b) 343 m/sec
c) 3000 m/sec
d) 4300 m/sec
Explanation: The velocity of sound in air at 20°C is 343 m/sec. The velocity of sound in bricks is 4300 m/sec while that in concrete is 4000 m/sec.
4. The intensity of sound is proportional to ______ of amplitude.
a) Square root
b) Cube root
Explanation: Intensity is the amount of wave energy passing through a unit area per unit time. The area taken is perpendicular to the direction of the propagation of the wave. The intensity of sound is proportional to the square of the amplitude.
5. Which of the following relations between loudness and intensity is correct?
a) I ∝ log L
b) I ∝ log L2
c) L ∝ log I
d) L ∝ log I2
Explanation: Loudness is related to intensity by the relation L ∝ log I where L is the loudness and I is the intensity of sound. The loudness of a sound is the degree of sensation which depends on the intensity of sound and the sensitivity of eardrums while intensity is purely a physical quantity.
6. Which law states that the magnitude of a sensation is directly proportional to the logarithm of the physical stimulus producing it?
a) Beer-Lambert law
b) Huygens–Fresnel law
c) Lorentz law
d) Weber and Fechner’s law
Explanation: Weber and Fechner’s law states that the magnitude of a sensation is directly proportional to the logarithm of the physical stimulus producing it. For example, loudness which corresponds to the magnitude of the sensation is proportional to the logarithm of the intensity of the sound.
7. The intensity of sound depends on the ear of the listener.
Explanation: Intensity of sound is independent of the ear of the listener. However, loudness does depend on the ear of the listener. There is a possibility that the same listener gives different judgements about the loudness of sounds having the same intensity but different frequencies.
8. _________ is the number of cycles made by a sounding body per unit time.
Explanation: Frequency is the number of cycles made by a sounding body per unit time. It is used to distinguish a shrill sound from a grave one. It is the reciprocal of the time period.
9. The amount of sound transmitted outside a room depends on the surface while the amount of sound reflected or absorbed depends on the sound insulation properties of the surface.
Explanation: There are three phenomenons which happen when sound waves strike the surface of a room. These are reflection, absorption and transmission. The amount of sound transmitted outside a room depends on the sound insulation properties of the surface while the amount of sound reflected or absorbed depends on the surface.
10. Which of the following statements is correct?
a) Pitch of the sound increases with increase in frequency
b) Pitch of the sound decreases with increase in frequency
c) Decibel is equal to 1/100 of bel
d) Increase in the amplitude of the sound decreases the intensity
Explanation: Pitch of the sound increases with increase in frequency. Decibel is equal to 1/10 of bel. Increase in the amplitude of the sound increases the intensity.
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