A stereo has a measured sound level of 120dB (a) what is the intensity of this s

Question

A stereo has a measured sound level of 120dB (a) what is the intensity of this sound in w/m^2? (b) The measurement of the sound level in part (a) above was made by a person standing at the point of measurement. Should this person have been wearing ear protection at the time of the measurement? Support your answer by quoting the sound level in dB above which it is recommended that ear protection be worn. (c) If stereo volume is adjusted to give an intensity of 1.2 Wm^-2 at a distance of 4m from the speaker what would be the required power output? (d) If there is a salt water fish tank in the same room as the stereo, what is the speed of the sound waves that travel through the water (e) A sound wave is what type of mechanical wave?

Explanation / Answer

We are given =120dB

a)We use equation,

= 10dB*log10(I/I0)

Plugging values,

120=10log[(I/(10^-12)]

12=log[(I/(10^-12)]

I= 1.0 W/m^2

b)

Hearing protection level = 85dB

hence the person must have wearing ear protection while measuring the sound level of 120dB.

c)

Intensity = power*Area

Power = Intensity*Area

P=I*4r^2

Plugging values,

P=1.2*4*3.14*4^2

P= 241.15 W

d)

Speed of sound in salt water = 1500m/s

e)

Since particle motion is parallel to wave motion hence sound wave is longitudinal wave.

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