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Physics Homework Help?

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At a rock concert, a dB meter registered 126 dB when placed 2.1 m in front of a loudspeaker on the stage. The intensity of the reference level required to determine the sound level is 1.0×10−12W/m2.

Part A
What was the power output of the speaker, assuming uniform spherical spreading of the sound and neglecting absorption in the air?
 
Part B
How far away would the sound level be 82 dB?

 

asked Nov 28, 2015 in PHYSICS by anonymous

2 Answers

0 votes

(A)

Step 1:

The intensity of the sound in decibels is image.

The reference level intensity of the sound is .

The loud speaker is placed at a distance of image.

The sound is spreading in uniform spherical.

The intensity of sound is image, where image is output power and image is area.

Find the intensity of sound.

The intensity of sound in decibels is , where image is intensity of sound and image is the reference level intensity of the sound.

image

image

image

image

image

image

image

image.

Step 2:

The area of the uniform spherical is image.

image

image.

Substitute image and image in image.

image

image

image.

The output power is image.

Solution:

The output power is image.

answered Nov 28, 2015 by Sammi Mentor
edited Nov 28, 2015 by Sammi
0 votes

(B)

Step 1:

The intensity of the sound in decibels is image.

From part (A): The output power is image.

Find the intensity of the image sound.

The intensity of sound in decibels is , where image is intensity of sound and image is the reference level intensity of the sound.

image

image

image

image

image

image

image

image.

Step 2:

The sound is spreading in uniform spherical.

Find the distance between loud speaker and decibel register.

The intensity of sound is image, where image is output power and image is area.

The area of the uniform spherical is image.

image

image

image

image

image.

The distance between loud speaker and decibel register is image.

Solution:

The distance between loud speaker and decibel register is image.

answered Nov 28, 2015 by Sammi Mentor
edited Nov 28, 2015 by Sammi

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