Talk:Sound power level

References Added
This article is in good shape so far as the basic physics is concerned but it was without good references so I have added two references from two very notable physics departments to support this article via the Wiki verifiable references standard. I included both references because there is a difference between sound power and sound intensity and the Wiki readers should be aware of that (this article itself however does not confuse the two - it does a great job :) I have also added an additional external link which is an interesting study published by the Journal of the Acoustical Society of America on this very subject. Cheers, Astrobayes 22:43, 23 June 2006 (UTC)


 * Excellent! — Omegatron 04:00, 24 June 2006 (UTC)

SPL vs. SWL
As the article starts out mentioning, SPL means Sound Pressure Level, whereas Sound Power Level is abbreviated SWL. So correct me if I'm wrong, but when speaker manufacturers mention 93 dB SPL 1W/1m, are they not referring to Sound Pressure Level? In that case, this section should be in the Sound pressure article (which details SPL), instead of this.130.227.121.251 (talk) 19:44, 19 November 2009 (UTC)

You are correct. I deleted that section, as this is covered in the loudspeaker article, and really has little to do with sound power level. Ereuter (talk) 01:41, 28 October 2010 (UTC)

Error in formula
It seems the formula connecting SPL and SWL has the wrong sign. I changed it right away, but since it is such an important and yet hard to notice change, I'll just post it here for review. I changed: $$ \mathit{SPL} = \mathit{SWL}+10\, \log_{10}\left(\frac{4\pi r^2}{S_0}\right) $$ to: $$ \mathit{SPL} = \mathit{SWL}-10\, \log_{10}\left(\frac{4\pi r^2}{S_0}\right) $$ It seems clear that SPL should decrease with increasing distance to the sound source. 130.227.121.251 (talk) 19:49, 19 November 2009 (UTC)

I just changed this to restore the plus sign, but invert the ratio. The reference for sound power level is derived from the reference for sound pressure level, which is the threshold of hearing (2E-5 Pa). The idea is that sound pressure level is sound power level divided by the surface area of a sphere. The logical place for the surface area is in the denominator. There is also a directivity factor, Q, that can be included, but that level of intricacy should probably be relegated to the sound pressure level article. Ereuter (talk) 23:53, 27 October 2010 (UTC)

Wolframalpha calculates values 11 dB lower than values in the table
This link calculates SPL of .001 W at 1 m; the result is 78.99 dB. The table shows 90 dB. (Larger input values are not accepted by Wolframalpha, as they are considered out of range.) --Onerock (talk) 02:54, 25 January 2010 (UTC)

The calculator is correct. The table give sound POWER level, which is not dependent on distance. Sound PRESSURE level at 1 m from a source is 11 dB less than the sound power level. Ereuter (talk) 01:47, 28 October 2010 (UTC)