Is there a formula for calculating SPL?

[Chantelle]

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

 

[Gordianus]

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)

 

[Chantelle]

Thanks, howvere, at risk of sounding completely stupid what is or what value is p?

 

[Gordianus]

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.

 

[Chantelle]

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

 

[Gordianus]

I said SPL=20log(p/pref)=20log(20/20)=0 dB
You used the inverse function.
Are you acquanteid with logarithms?

 

[Chantelle]

No. I'm a musician doing a course in sound technology :( x

 

[Gordianus]

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.

 

[Chantelle]

No offence taken at all. Very grateful for your help, thankyou x