Why Does Doubling Sound Sources Not Simply Double the Decibel Level?

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Homework Help Overview

The discussion revolves around the relationship between sound intensity levels and the effects of adding multiple sound sources. The original poster presents a scenario involving two sound sources, each producing a sound intensity level of 30 dB, and questions the resultant level when both sources are active.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the mathematical relationship between sound intensity and decibel levels, questioning why the resultant level is calculated as 33 dB instead of a higher value based on amplitude considerations. There is also discussion about the correlation of the sound sources and its impact on the resultant intensity.

Discussion Status

Participants are actively engaging with the problem, raising questions about the assumptions regarding the correlation of sound sources and the implications for the resultant decibel level. Some guidance is provided regarding the addition of intensities versus amplitudes, but no consensus has been reached on the interpretation of the results.

Contextual Notes

There is an underlying assumption about the correlation of the sound sources, which is not explicitly defined. The discussion also touches on the mathematical properties of logarithms in the context of sound intensity calculations.

somecelxis
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Homework Statement


A source prodeuces sound of intensity level of 30dB .If another source prodeuces sound at the same time , what's the resultant level?

Homework Equations


The Attempt at a Solution



the ans is 10 log (2##I_1## / (##I_0##)) = 33dB , but why not = 10 log (4##I_1## / (##I_0##)) .. beacuse when 2 sound waves superposed , the resultant amplitude is A+A= 2A , I is directly proportional to (A^2) ...
 
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Are the two sounds correlated (e.g., in phase) with each other? The sum of the two will only have amplitude A + A (and therefore +6 dB) if they are perfectly in phase with each other. In general they're assumed uncorrelated (they have nothing to do with each other), and so you add the intensities and get +3 dB.
 
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olivermsun said:
Are the two sounds correlated (e.g., in phase) with each other? The sum of the two will only have amplitude A + A (and therefore +6 dB) if they are perfectly in phase with each other. In general they're assumed uncorrelated (they have nothing to do with each other), and so you add the intensities and get +3 dB.

it's not 3db am i right? the intensity now it's 2I ?
 
33 dB is +3 dB relative to the original 30 dB, right?

Hint: log102 = ?
 

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