Sound level Question....plz help!!!!?

2009-06-07 6:56 pm

Jack's hearing test revealed that he needed a sound level of 20 dB to detect sounds at 2000 HZ. Sam's hearing test revealed that he needed a sound level of 40 dB to detect sounds at the same frequency If the normal sound level for testing is 15 dB, how much greater than normal were the sound intensities Jack and Sam needed to detect the sound?
plz explain, i don't mind if u give me the answer or not, i just want to understand how to do it , ty!!

回答 (1)

[匿名]

2009-06-09 2:36 pm

✔ 最佳答案

First you have to convert the sound level to sound intensity. For that there is this equation.

L = 10 log (I / Io)

L - Sound level in decibel
I - Intensity of sound
Io = 10^-12 Wm^-2

Intensity of normal sound,
L = 10 log (I / Io)
15 = 10 log (I1 / 10-12)
I1 = 3.1623 x 10^-11 Wm^-2

Intensity of sound jack needed,
L = 10 log (I / Io)
20 = 10 log (I2 / 10-12)
I2 = 1.000 x 10^-10 Wm^-2

Intensity of sound sam needed,
L = 10 log (I / Io)
40 = 10 log (I3 / 10-12)
I3 = 1.000 x 10^-8 Wm^-2

Intensity of sound jack needed to detect the sound is 6.8377 x 10^-11 Wm^-2 [1.000x10^-10 - 3.1623x10^-11] greater than normal sound intensity.

Intensity of sound sam needed to detect the sound is 9.9684 x 10^-9 Wm^-2 [1.000x10^-8 - 3.1623x10^-11] greater than normal sound intensity.

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