Is there a formula for calculating SPL?

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Discussion Overview

The discussion revolves around the calculation of Sound Pressure Level (SPL), specifically exploring the formula used to derive SPL from sound pressure and the reference pressure level. Participants share their understanding of the concepts involved, including the relationship between sound pressure and SPL.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant inquires about a formula for calculating SPL, mentioning frequency, dB level, and the reference pressure of 20 micro Pascals.
  • Another participant provides the formula SPL = 20 log(p/pref) and explains that 20 micro Pascals is the reference pressure level for 0 dB SPL.
  • A participant seeks clarification on the variable 'p' in the formula, expressing uncertainty about its meaning.
  • It is suggested that knowing either the pressure or SPL allows for the calculation of the other, while lacking both presents a significant challenge.
  • One participant calculates sound pressure based on a given SPL of 20 dB and the reference pressure, arriving at a value of 200 micro Pascals, and seeks confirmation of this calculation.
  • Another participant points out a misunderstanding regarding the use of the formula and confirms that the calculated SPL of 20 dB is indeed correct when the acoustic pressure is 200 micro Pascals.
  • A participant identifies themselves as a musician studying sound technology, indicating a potential gap in mathematical knowledge related to logarithms.

Areas of Agreement / Disagreement

The discussion shows some agreement on the formula for SPL and the reference pressure level, but there is uncertainty regarding the calculations and the understanding of logarithmic functions. Participants do not reach a consensus on the clarity of the mathematical concepts involved.

Contextual Notes

There are indications of missing assumptions regarding the understanding of logarithmic calculations and the implications of sound pressure in relation to SPL. The discussion reflects varying levels of familiarity with the mathematical concepts involved.

Who May Find This Useful

This discussion may be useful for individuals studying sound technology, acoustics, or related fields, particularly those seeking to understand the relationship between sound pressure and SPL calculations.

Chantelle
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Hi. Is there a formula for calculating SPL?

The information I have is Frequency of pitch, dB level of pitch and 0dB as 20uPa.

TIA
 
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The reference pressure level (pref), which defines the threshold of hearing for an average healthy person, is 20 micro Pascals. That pressure is the 0 dB SPL. Other values are computed as:

SPL=20 log(p/pref)
 
Thanks, howvere, at risk of sounding completely stupid what is or what value is p?
 
If you know the pressure, you can compute the SPL. If you know the SPL, you can calculate the pressure. If you know neither of them, you're in serious trouble.
 
I think I probably am! :)

Looks like its the sound pressure i need.

Do you think this is correct?

Source is 20dB and pref is 20uPa

Sound pressure = 20 x 10^(20/20) = 200uPa??

Thanks for your time and help x
 
I said SPL=20log(p/pref)=20log(20/20)=0 dB
You used the inverse function.
Are you acquanteid with logarithms?
 
No. I'm a musician doing a course in sound technology :( x
 
My apologies, I meant no offense. By the way, your example was right. When I read it I was too tired and I misunderstood what you had written. If the acoustic pressure is 200 micro Pascals the SPL is 20 dB indeed.
 
No offence taken at all. Very grateful for your help, thankyou x
 

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