Engineering Questions with Answers - Multiple Choice Questions
Reverberation – 1
How are sound waves with a frequency of 20Hz to 20,000Hz termed?
a) Inaudible sounds
d) Audible sound
Explanation: Sound waves below the frequency of 20Hz are infrasonics. Sound waves above 20,000Hz are ultrasonics. Both are inaudible. Sound waves between 20Hz to 20,000Hz are audible sounds.
Sound of mosquito produces high pitch than the sound of a lion.
Explanation: Pitch depends directly on the frequency of incident sound waves. Though pitch is directly related to frequency, they are not the same. In general, frequency is physical quantity whereas the pitch is physiological quantity.
What is the quantity that helps us distinguish a particular voice of a singer from the voice of many singers?
Explanation: The timbre or quality of sound is one which helps us to distinguish between musical notes emitted by different musical instruments or voices, even though they have the same pitch and loudness.
Sensitivity increases with a decrease in intensity.
Explanation: L = k log I
Differentiating the above equation,
dL/dI = k/I
Therefore sensitivity decreases with an increase in intensity.
What happens if the reverberation time is too large?
a) The sound becomes inaudible
b) Echoes are produced
c) Frequency becomes high
d) The sound becomes infrasonic
Explanation: Reverberation is the time taken for the sound to fall below the minimum audibility measured from the instant when the source stopped sounding. Therefore if the reverberation time becomes too large it produces echo.
What will happen when sound is focussed to a particular area?
a) Echoes are produced
b) Sound becomes inaudible
c) Interference occurs
d) Frequency of sound becomes high
Explanation: When sound waves are produced in a hall, it reaches the observer directly as well as after reflections from walls, floors, ceilings etc. Thus when sound is focussed to a particular area it is possible that interference is produced between the waves, which in turn affect the originality of the sound.
Sound produced from equally spaced steps in a stair case at regular intervals is due to which effect?
a) Reverberation effect
b) Noise effect
c) Absorption effect
d) Echelon effect
Explanation: If there is a regular repetition of the original sound to the observer then the effect is called Echelon effect. Sound produced by equally spaced steps in stairs at regular intervals produce echelon effect.
What happens when window panel sections of the wooden portions are thrown into vibrations to produce new sounds?
a) Vibrations are produced
b) Resonance occurs
c) Echoes are produced
d) Absorption occurs
Explanation: Resonance occurs when a new sound not of frequency matches with standard audio frequency. When window panel sections, of the wooden portions are thrown into vibrations to produce new sounds it results in interference between original sound and created sound. This will create a disturbance to the audience.
A cinema theatre has a volume of 750m2. What should be the total absorption in the theatre if the reverberation time of 1.5seconds is to be maintained?
a) 835 open window units
b) 1125 open window units
c) 500 open window units
d) 750 open window units
Explanation: Reverberation time = 0.167/Σas
Total absorption Σas = 0.167V/T
Total absorption = 835 open window units.