Acoustic Materials And Meta Materials

A). The wave is get diffracted.

B). Partly get reflected.

C). Partly get transmitted.

D). All the above.

A). Source based

B). Path based

C). Receiver based

D). Any one of the above

A). Near field

B). Far field

C). Diffusive filed

D). Open field

A). Porous-fibrous sound absorbers

B). Panel sound absorbers

C). Helmholtz resonators

D). All the above.

A). Amplifier

B). Signal conditioner

C). Sound level meter

D). Signal Analyser

A). octave bands

B). 1/3 octave bands

C). 1/6 octave bands

D). Any one of the above.

A). 1x10-5 Pa .

B). 2x10-5 Pa.

C). 20 Pa .

D). 200 Pa.

A). Sound pressure level

B). Sound intensity level

C). Sound power level

D). All the above

A). same frequency

B). same wave form

C). constant phase difference

D). All the above

A). Reflect less

B). Transmit less

C). Dissipate more

D). All the above

A). Decrease in transmission coefficient of the enclosures wall materials

B). Increase with absorption coefficient of the lining material

C). Increase with wall material thickness

D). All the above

A). Barriers

B). Enclosures

C). Porous absorbers

D). Helmholtz resonators

A). fn=c/2L

B). fn=nc/4L

C). fn=nc/2L

D). fn=nc/L

A). the ratio of sound intensity absorbed by the material to the sound intensity incident on the material.

B). the energy absorbed is the fraction of the incident energy that is lost in the process of reflection

C). lost of incident energy in the process of reflection.

D). All the above

A). Opaque/semi opaque materials are used for acoustic barriers

B). Barriers for outdoor is mostly use in the free field conditions

C). Barriers are much effective in direct sound field compared to the reflected sound file.

D). None of the above

A). Insertion loss of a material is the difference in sound pressure levels at the receiver point without and with the material.

B). Nosie reduction is the difference between the sound pressure level before and after passing through a barrier material.

C). Transmission loss is the difference between the incident sound intensity level and transmitted sound intensity level when the sound waves hit that material.

D). None of the above.

A). Vary with space but not with time.

B). Vary with time but not with space.

C). Vary with the both time and space.

D). All the above.

A). ratio of complex pressure amplitudes between the transmitted and incident waves.

B). lost of incident energy in the process of reflection.

C). ratio of complex pressure amplitudes between the reflected and incident waves.

D). Both b and c.

A). Oscillate at fixed amplitude not vary with time, vary only with the space.

B). Oscillate at fixed amplitude not vary with Space, vary only with the time.

C). Oscillate at fixed amplitude varies with space and time.

D). None of the above.

A). Blue noise

B). Pink noise

C). White noise

D). All the above

A). Is the number of complete wave cycles in radians per unit time.

B). Is the number of complete wave cycles in radians per unit spatial dimension.

C). Is the number of complete wave cycles in radians per sec.

D). None of the above.

A). their pressure difference

B). the ratio of their intensities

C). both a & b

D). their absolute pressures

A). Blue noise

B). Pink noise

C). White noise

D). All the above

A). 1dB

B). 5dB

C). 10dB

D). 20dB

A). Lp = 10 log10 (prms /Pref)

B). Lp = 10 log10 (Irms/Iref)

C). Lp = 20 log10 (prms /Pref)

D). Both b and c

A). 60dB

B). 80dB

C). 100dB

D). 140dB

A). Viscous shear

B). Friction

C). Scattering

D). All the above

A). Difference of upper and lower frequencies

B). Average of upper and lower frequencies

C). Geometric mean of upper and lower frequencies

D). None of the above

A). has constant amplitude on any plane perpendicular to the direction of wave propagation.

B). has constant phase on any plane perpendicular to the direction of wave propagation.  

C). has constant amplitude and phase on any plane perpendicular to the direction of wave propagation.

D). All the above.