Centre for Educational Technology
Subject: Audio System Engineering
Time: 2:00 Hours
Code: ET60006
Full Marks [5x2+4x10] = 50
Answer all the questions
PART-A
1. An acoustic pressure wave with an amplitude P is incident on a surface of a liquid from air. If the velocity of
sound c1 in air is 350 m/s and c2 liquid is 1000 m/s find out the value of the critical angle.
2. If the intensity of 1 kHz sound wave in air is 40dBm. Find out the value of root mean square pressure?
Where density of air is ρ0 =1.21 kg/m3 and sound velocity in air is c=350 m/s
3. The equation of a plane wave is given in equation no.-1. Calculate the Magnitude of the Propagation
Vector
4. In a sound system equalizer, gain for a particular frequency band is raised by 12dB calculate the percentage
increase of Sound Pressure Level(SPL) for that particular frequency band
5. Two source of sound system producing same frequency sound. The overall intensity of one source is 20dB
and other is 21dB. Can a normal hearing ability human being differentiate the loudness of the two sources?
Write the reason.
1.
2.
3.
4.
Answer all the questions
PART-B
Diaphragm of a loudspeaker oscillated by a sinusoidal force of amplitude 2N.
(a) Find out the driving force frequency for which phase angle between displacement and speed is π/4.
(b) Find out the maximum speed of the Diaphragm at that phase angle.
Where mass of the loudspeaker diaphragm is 0.5g/s, stiffness is 100N/m and mechanical resistance is
1.2kg/s.
In an auditorium at some location the pressure amplitude and particle speed of a 1000 Hz sound wave in
air are measure to be 4 Pa and 0.01 m/s respectively. Consider that sound is traveling as spherical wave.
Where density of air ρ0=1.21 kg/m3 and velocity of sound in air c = 340m/s.
(a) Determine the distance of the location from the source.
(b) Calculate the absolute magnitude of the specific acoustic impedance and phase angle between
pressure and particle speed
An acoustic tile panel is characterized by a normal specific acoustic impedance of Zn=900-j1200 pa.s/m. A
sound wave was indicated from air to the acoustic tile
(a) Determine the power reflection coefficient for an incidence angle of 600
(b) Calculate the power reflection coefficient for normal incidence.
A sand bottom in seawater is characterized by ρ2=1600kg/m3and c2=1600m/s.
(a) Calculate the angle of incidence for which intensity reflection coefficient equal to 0.25
(b) Determine the intensity transmission loss in dB
Where seawater is characterized by ρ1=1.027g/cm3and c1=1400m/s.
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