This is the Coaching materials in Acoustics Part 3 as one topic in ECE Board Exam taken from various sources including but not limited to past Board Examination Questions in Electronic System and Technologies (EST), Communications Books, Journals and other Communications References. This particular Coaching Notes in Communications Engineering has random Questions and Answers in random topics. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.
Acoustics Coaching Materials Part 3
1. Sound equalization means
boosting or reducing some frequency components to achieve a desired effect.
2. A type of equalizer in which all the filter’s parameters can be varied. Parametric equalizer.
3. An equalizer which uses a bank of closely spaced fixed-frequency band-pass filters to cover the entire audio frequency range.
Graphic equalizer.
4. The first sound heard by an observer.
Direct sound
5. Time delay of reflected sound which can be considered as early reflection.
20ms
6. an incident sound with an intensity of 16 mW/m^2 reflects a wall with an absorption coefficient of 0.9. Determine the intensity of the reflected wave. 1.6 mW/m^2
7. Unit of sound absorption
Sabine
8. The average absorption of a person is
4.7 sabines
9. Persistence of sound in an enclosed space, as a result of multiple reflections or scattering after the sound source has stopped.
10. Reverberation
11. The time elapsed for the sound to die away in an enclosed room.
reverberation time (reverberation)
12. The time considered to have a reverberation effect.
One millionth
13. the perceptible repetition of sound due to multiple reflection of sound waves between the walls of a room is called
echo.
14. A room in which the walls, floor, and ceiling can absorb very little sound, resulting in echoes.
Reverberation chamber.
15. Room whose boundaries absorb effectively all incident sound.
Anechoic room.
16. Resonant acoustic device consisting of air cavity connected to a larger space by a relatively small opening or neck.
Helmholtz resonator.
17. Sound reverberation is dependent on.
Listener position and room dimension
18. The distance between the sound source and the listener wherein the direct sound level is equal to the reverberant field.
Critical distance
19. Most people commonly receive an increase in sound level of
6 to 10 dB.
20. In a typical hi-fi system in a living room, which sound wave is the most dominant?
Reverberant field
21. A room which causes the sound to die away very quickly.
Dead room
22. A room which causes the sound to die away very slowly.
Live room
23. An electronic device used to produce special sound effects when it is held against the throat of the user
Sonovox
24. A temperature sensing device whose heat-absorbing properties are enhanced by subjecting it to acoustic vibrations.
Sonic thermocouple
25. An enclosure, usually a box or a can, for modifying the acoustic qualities of sound
sound chamber.
26. A transducer used for the purpose of picking up acoustic vibrations for detection or measurement applications.
Sound probe
27. Used as the sensing element of sound-pressure.
Diaphragm
28. A sound pressure transducer whose sensing diaphragm is used as one electrode of a capacitor.
Condenser microphone.
29. Carbon microphones use.
Variable resistance.
30. Ribbon microphone is an example of _____ microphone.
pressure-gradient
31. An underwater acoustic pressure sensor, that is actually a sound-to-electricity transducer.
Hydrophone
32. The transmitting and receiving device in a sonar.
Sound transceiver.
33. A sound transducer first achieved by Bell in magnetic form and later made practical by Edison’s use of hard-coal particles.
Loose-contact transducer.
34. A transducer with a coil that surrounds some portion of a magnetic circuit. The reluctance of the magnetic circuit is varied by the motion of a moving iron.
Moving-iron transducer.
35. Sound transducer whose generated potential is due to the oscillation of the coil within a uniform magnetic field.
Moving-coil transducer.
36. A special type of electrostatic microphone which holds polarization indefinitely without continued application of a polarizing potential.
Electrets microphone.
37. Sound transducer whose output potential is generated through the flexing of crystalline elements as it is acted by sound waves.
Piezoelectric
38. What property of a crystalline material is used in a crystal microphone?
The piezoelectric effect
39. An electroacoustic transducer that radiates acoustic power into the air. The acoustic waveform is equivalent to the electrical input waveform.
Loudspeaker.
40. Loudspeaker low frequencies response will be maximum if positioned in a room at the
corner.
41. Most loudspeakers today are of
moving-coil type.
42. The intensity characteristic of sound.
Loudness
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