Talk:Sound pressure level

Microphone: measures pressure or displacement?

i think some microphones are better thought of as displacement measurers instead of pressure measurers. is this true? - Omegatron 20:08, Jul 16, 2004 (UTC)

I can't see what the objective difference between these alternatives would be, given that the displacement e.g. of some membrane is directly caused by the pressure of a sound wave. Therefore, it seems to me that the question is meaningless. RPaschotta 10:49, 21 Nov 2004 (UTC)

Sound pressure amplitudes

When sound pressures are specified, one should be more clear about their definition: is it the peak pressure (i.e., the amplitude of a sinusoidal signal), or rather some rms (root-mean-square) value? This applies e.g. to the reference sound pressure specified in the article. Can anybody help? RPaschotta 10:49, 21 Nov 2004 (UTC)

merging

Sound measurements
Characteristic	Symbols
Sound pressure	p, SPL, LPA
Particle velocity	v, SVL
Particle displacement	δ
Sound intensity	I, SIL
Sound power	P, SWL, LWA
Sound energy	W
Sound energy density	w
Sound exposure	E, SEL
Acoustic impedance	Z
Audio frequency	AF
Transmission loss	TL

$Merging\ is\ really\ no\ good\ idea!\ \ \ SPL\ is\ not\ sound\ pressure.$

Look at the two articles. They're very closely related. I don't think they deserve two separate articles. - Omegatron June 30, 2005 13:53 (UTC)

We have SPL as a level [dB] an the sound pressure [Pa]. That is not closely related. If I look for level, I need no sound pressure. If I look for sound pressure, I need no level. The same is with sound level, with sound intensity level, with sound power level, and particle velocity level. Merging is not desirable. Look at the other languages. IT's always separated. Mike 20:08, June 30, 2005 (UTC)

Ok. There would still be redirects so if you look for SPL you will find sound pressure. Look at sound pressure. It already has a description of SPL in it! I don't think it is absolutely imperative to merge, though. Whatever. - Omegatron July 2, 2005 04:17 (UTC)

It has been suggested that this article or section be merged with particle velocity. (Discuss) That's no good idea. Keep it as it is. Ericd 13:22, Sep 02, 2005 (UTC)

Pressure and particle velocity are related (p = rho c u, Robert Urick's "Principles of Underwater Sound" (3rd edition), pp.11-12), but they are definitely not the same thing. Two articles are indicated, but each should note the relation. Wesley R. Elsberry 10:42, 9 April 2006 (UTC)

Sound pressure level has been redirected to the relevant section of sound pressure for a while, which I think is appropriate. Has the time come to redirect it again to the sound pressure level section of sound? I think that one longer article would be useful to avoid undue repetition. pheon 14:16, 24 October 2006 (UTC)

I'd say SPL is a specific way to represent sound pressure, so they should be in the same article. But sound pressure should have its own article, just like air pressure is distinct from air, blood pressure is distinct from blood, vapor pressure is distinct from vapor, etc. Otherwise we'd have to put all of the sound measurements and concepts into the sound article, and it would get crowded quickly. — Omegatron 12:46, 25 October 2006 (UTC)

Sound pressure level problem

The treatment of sound pressure level appears to be inconsistent with standard reference works across Wikipedia. Both Kinsler and Frey's "Fundamentals of Acoustics" (2nd edition) and Robert Urick's "Principles of Underwater Sound" (3rd edition) indicate that a measured intensity is a level (Urick p.15) or sound pressure level (K&F) relative to a reference effective pressure (K&F pp.125-126). Both of these sources recommend reporting decibels with an explicit listing of the reference effective pressure, like so: "74 dB re 20 micropascals", where the number and units following re is the reference effective pressure. I was working on the decibel article's misuse of SPL as if it specified a reference effective pressure when I realized that several other articles were similarly affected. I don't have time at the moment to correct all of them, but I will drop this comment into the discussion part of each article that I have come across so far with this problem. Level or sound pressure level in both these standard texts simply refer to a measurement in the sound field and are not indications of a specific reference pressure upon which the decibel is based. In other words, "dBSPL" is an incorrect means of attempting to refer to the in-air reference effective pressure. In no article thus far have I seen the "dBSPL" usage tied to an authoritative source. By contrast, the "dB re" formalism is common to both standard reference works that I have cited. Wesley R. Elsberry 10:42, 9 April 2006 (UTC)

Other sites using the "dB re" formalism: Oceans of Noise (explicit in defining SPL and SIL in terms of "dB re"), SURTASS LFA, NIST listing SPL in terms of "dB re", and Acoustic Impacts on Marine Mammals. But the best thing I've found has to be ASACOS Rules for Preparation of American National Standards in ACOUSTICS, MECHANICAL VIBRATION AND SHOCK, BIOACOUSTICS, and NOISE, which states:

3.16 Unit symbols

3.16.1 When to use unit symbols

In the text of the standard, the unit symbol for a quantity shall be used only when the unit is preceded by a numeral. When the unit is not preceded by a numeral, spell out the name of the unit. In text, even when a numerical value is given, it is desirable to spell out the name of the unit. Moreover, the name shall be spelled out when it first appears in the text, and more often if the text is lengthy.

Thus, in text write "...a sound pressure level of 73 dB; or "...a sound pressure level of 73 decibels." Do not write "sound pressure level in dB"; the correct form is "sound pressure level in decibels." Do not write "dB levels", "dB readings", or "dB SPL."

Levels or readings are not of decibels; they are of sound pressure levels or some other acoustical quantity. Write out the word "decibel" for such applications, and be sure that the word 'decibel' follows, not precedes the description of the relevant acoustical quantity.

The guidelines given for the National Standards clearly excludes the use of "dB SPL". Wesley R. Elsberry 17:05, 9 April 2006 (UTC)