Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Overall Sound Pressure Level calculation

Status
Not open for further replies.
Dan90

Dan90

Automotive
Joined
Apr 19, 2014
Messages
40
Location
IT
Hello to everybody,

I am a bit confused about the calculation of an OSPL of a pressure spectrum.

From what I learned, I know that the OSPL should be a number describing how much energy is related to the spectrum under consideration. Nothing special so far, but I read about two formulas for its calculation:

1) 20 log[ (sq.root (integral(p2 df))/pref), the integral being between fmin and fmax;

2) 20 log[ (sq.root (sum(p2))/pref);

Now, in my opinion, the first expression should be more suitable to the OSPL calculation as it involves directly the energy associated with the spectrum (thanks to the integral of the squared pressures).

Can someone give me some more detailed explanation?

Best Regards,

Dani

 
Sort by date Sort by votes
Hi Greg,

thank you very much for the reply.

I think you are right on the use of the second formula only when the spectrum is expressed in bands.

In my opinion this is due to the fact that when I convert a PSD from narrow band to, for example, 1/3 octave bands, the values I get for each band is already the area under the PSD spectrum in that specific band. In oder words, when I convert the spectrum in 1/3 octave bands I already get information about the energy of the signal in that band.

Consequently, in order to calculate the overall SPL when the spectrum in expressed in 1/3 octave band it would be erroneous to use the first formula as the values of the "new spectrum" are already the results of integrals. In this case, it would be necessary to just add up all the values in each band (second formula)

To prove that, I calculated the orverall SPL of a linear spectrum with the first formula. Then I have converted the linear spectrum to 1/3 octave band spectrum calculating the overall by means of the second formula: obviously the two numbers were the same...

What do you think?

Best regards,

Dani
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

Cheetos
  • Locked
  • Question Question
Find sound pressure at the source
Replies
5
Views
471
GregLocock
GregLocock
Leebanana
  • Locked
  • Question Question
Question about Sound Power Levels and measured Sound Pressure Levels in dB(A)
Replies
2
Views
450
hydtools
hydtools
midsidenode
  • Locked
  • Question Question
equivalent pressure
Replies
6
Views
765
GregLocock
GregLocock
hirschaplin
  • Locked
  • Question Question
Approach to predict the noise level of a rotary machine
Replies
1
Views
410
GregLocock
GregLocock
hirschaplin
  • Locked
  • Question Question
Approach to predict noise level and how to communicate it
Replies
3
Views
755
geesaman.d
geesaman.d

Part and Inventory Search

Sponsor

Back
Top