This set of Audio Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Characteristics of a Microphone”.
1. What is termed as a transducer that converts acoustic sound pressure variation into the electrical signal of same amplitude, frequency and in the same proportion as pressure variations?
a) Microphone
b) Sensitivity
c) Distortion
d) Directivity
View Answer
Explanation: Microphone is termed as a transducer that converts acoustic sound pressure variation into the electrical signal of same amplitude and frequency, in the same proportion as pressure variations. In any sound recording and radio transmission system, the first element which is used to convert acoustic wave into electrical wave for processing is the microphone.
2. What is defined as the electrical signal in audible range (20 Hz to 20 KHz) in a microphone?
a) Video signal
b) Audio signal
c) Transmission signal
d) Mixed signal
View Answer
Explanation: Audio signal is defined as the electrical signal in audible range (20 Hz to 20 KHz). The globally accepted standard range of audible frequencies is 20 to 20,000 Hz, although the range of frequencies individual hear is greatly influenced by environmental and other factors.
3. Sensitivity is also measured in dBm that is power ratio with reference to 1 mW in a microphone.
a) True
b) False
View Answer
Explanation: Microphone sensitivity specification tells how much electrical output microphone produces for a certain sound pressure input (dB). Thus, sensitivity is also measured in dBm that is the power ratio with reference to 1 mW.
4. What is termed as the ratio of output of microphone in the presence of sound to output of microphone in the absence of sound with logarithmic base of 20?
a) Frequency response
b) Distortion
c) Directivity
d) Signal-to-noise ratio
View Answer
Explanation: Signal-to-noise ratio is defined as the ratio of output of microphone in the presence of sound to output of microphone in the absence of sound with logarithmic base of 20.
S / N = 20log output in presence of sound / output in absence of sound
5. Frequency response of a microphone is defined by the bandwidth of audio frequency in the output of the microphone within ± 5 dB of output at 100 Hz.
a) True
b) False
View Answer
Explanation: Frequency response of a microphone is defined by the bandwidth of audio frequency in the output of the microphone within ± 1 dB of output at 1000 Hz. In audible range of 16 Hz to 20 KHz a microphone which gives flat response within ± 1 dB is considered good for Hi-Fi audio systems.
6. What is related to uneven response to audio signals in microphone?
a) Distortion
b) Directivity
c) Frequency response
d) Signal-to-noise ratio
View Answer
Explanation: Distortion in microphone is related to uneven response to audio signals. Besides the frequency distortion the microphone accounts to two more distortions, namely non-linear and phase distortion.
7. What should be the distortion to maintain the quality of microphone and Hi-Fi systems?
a) Less than 5%, less than 1%
b) Less than 10%, less than 77%
c) Less than 100%, less than 45%
d) Less than 1000%, less than 97%
View Answer
Explanation: Nonlinear distortion is directly proportional to the amplitude of audio signals. Thus, to maintain the quality of microphone such a distortion should be less than 5% and for Hi-Fi (High Fidelity) system distortion is kept less than 1%.
8. Which is the correct expression for directivity in a microphone?
a) D = E/E0
b) D = E1/E0
c) D = E/E1
d) D = E2/E0
View Answer
Explanation: Directivity is defined as the ratio of the actual output when placed in the direction of maximum sound pressure to the output which an omnidirectional microphone in the same direction would have given, keeping the sound intensity constant. The expression for directivity is D = E/E0
Where,
E = actual output in the direction of maximum output
E0 = output in that direction if microphone is omnidirectional.
9. What is the percent of lobe present in rear of supercardioid microphone?
a) 25, 75
b) 37, 63
c) 20, 89
d) 67, 99
View Answer
Explanation: Super cardioid patterns are obtained with the contribution of omnidirectional and bidirectional microphone in proportion of 37-63 percent respectively. The polar representation of super cardioid microphone is,
R = 0.37 + 0.63 cosθ (lobe present in rear).
10. What is the percent of broader lobe present in rear of hypercardioid microphone?
a) 67, 99
b) 20, 89
c) 37, 63
d) 25, 75
View Answer
Explanation: Hyper cardioid pattern is obtained with the combination of omnidirectional and bidirectional microphone in series when the contribution is 25-75 percent respectively. The polar representation of hyper cardioid microphone is,
R = 0.25 + 0.75 cosθ (broader lobe present in rear).
11. Which is the correct expression for the output impedance of microphone?
a) Ω
b) λ
c) θ
d) v
View Answer
Explanation: A microphone has output impedance which is represented in ohms (Ω). This is important parameter to determine the type of matching transformer to transfer power efficiently from microphone to transmission line followed by amplifier.
Sanfoundry Global Education & Learning Series – Audio Engineering.
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