Bob plugs his guitar into his 35 W guitar amplifier, turns it all the way up, an
ID: 2177756 • Letter: B
Question
Bob plugs his guitar into his 35 W guitar amplifier, turns it all the way up, and plays a 390 Hz note. If he is standing 5 m away from it:(Note: For this problem, you may assume all of the amplifier's energy goes into the sound waves, and that these waves are approximately isotropic.)
a.) What is the intensity of the sound wave at this distance?____W/m2
b.) How loud is this in dB?____dB
c.) What is the displacement amplitude (smax) of this sound wave?____?m
(If he instead played a lower frequency note, this would be .)
d.) What is the pressure amplitude (Pa) of this sound wave?____Pa
(If he instead played a lower frequency note, this would be .)
e.) Now, if Bob increased his distance from the speaker by a factor of 5 times, by what factor would each of the following be affected?
(Hint: Use proportionalities to greatly minimize your work!)
Inew =____
Explanation / Answer
A. intensity=Power/area given by 30 W/ 4*pi*5^2 B.