How Do You Calculate Sound Intensity from a Decibel Level?

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Homework Help Overview

The problem involves calculating sound intensity from a given decibel level, specifically using a sound-level meter reading of 45 dB at a distance of 150 mm from a sound source. The original poster attempts to apply the equation for sound intensity levels but encounters discrepancies in the results.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the application of the intensity level equation and question the correctness of the original poster's calculations. There is an exploration of unit conversions and potential misunderstandings regarding the intensity values.

Discussion Status

Some participants have provided guidance on the calculations, noting possible issues with unit conversions. There is a recognition of differing interpretations of the results, but no explicit consensus has been reached regarding the correct intensity value.

Contextual Notes

Participants are considering the implications of using different units for intensity, such as the possibility of results being expressed in nanowatts per meter squared instead of watts per meter squared. The original poster expresses uncertainty about their calculations and seeks clarification.

alkhan22
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Homework Statement



A sound-level meter placed 150 mm from a small sound source records a reading of 45dB. What is the intensity at that point.

Homework Equations



I m using this equation IL = 10 log(I/I.) where I. is the lowest intensity i think which should be 10^-12 W/m^2.

The Attempt at a Solution



I have used the above equation to find the intensity but i get different answer which is 3.16 x 10^-8. but the correct answer given is 31.6 w/m square.

I will be very thankful if some body can hel as this is my 1t question in this forum. please let me know if i have missed something.
 
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can you show how you arrived at your answer?
 
this is how i got my answer.

45= 10[logI - Log10^-12]
4.5= LogI +12
-7.5 = log I

BECAUSE THE BAS WAS 10 SO

10^-7.5 = 3.1622 X 10^-8
 
that looks correct. it seems that the problem is one of mixing up units. the correct solution you have may be in units of nanowatts per meter squared.
 

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