# Talk:Sound power

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## Z = c · ρ - Wrong!?

The table at Sound power with plain sound waves reads the following:

Symbol Units Meaning
Z = c · ρ N·s/m³ acoustic impedance
p Pa sound pressure
ρ kg/m3 density of air
c m/s speed of sound

Shouldn't it be Z = p/c, since Pa = N/m2 ?

Because

(m/s) · (kg/m3) = kg / (m2·s)   != N·s/m3

(N/m2) / (m/s)  = (N/m2) · (s/m) = N·s/m3


Or did I miss something?

/Lord E (talk) 14:09, 14 September 2008 (UTC)

This is correct.

Specific acoustic impedance is ${\displaystyle Z=\rho _{0}c_{0}}$ (not sure why the ρ is funky in the math here.

Units work out as ${\displaystyle {\frac {kg}{m^{3}}}{\frac {m}{s}}=(kg{\frac {m}{s^{2}}}){\frac {s}{m^{3}}}=N{\frac {s}{m^{3}}}}$ --67.188.6.157 (talk) 08:01, 14 April 2010 (UTC)

## Merger proposal

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section. A summary of the conclusions reached follows.
Clear agreement on merge. -- P 1 9 9 • TALK 13:55, 22 March 2011 (UTC)

Sound power level should be merged into this article. --TheJokari (talk) 13:02, 25 September 2008 (UTC)

• Agree. The level of sound power is an important aspect, but not enough to give it its own article. Binksternet (talk) 20:25, 25 September 2008 (UTC)
• Agree. Sound power level is a ratio of sound power, and should be considered as part of the same topic Sam Lacey (talk) 20:09, 1 November 2009 (UTC)
• Agree Sound power level is just an expression of sound power in decibels (hence the use of the word level). It would be an easy merge - I think that Kvng is thinking of intensity, which is power over area. I disagree with 220.101.28.25 that sound pressure (or sound pressure level) and sound power should be combined. Ereuter (talk) 23:43, 27 October 2010 (UTC)

The above discussion is closed. Please do not modify it. Subsequent comments should be made in a new section.

## Threshold of pain?

I was wondering if on the "Sound power and sound power level of some sound sources" table, for the 120 dB row, if we could add the threshold of pain. There are various definitions for the threshold, but since 120 seems to be the most common, I think it should be included. Also, just for consistency's sake, since the auditory thresholds are included, why not include the threshold of pain? I just wanted to make sure it would be ok to add. Thanks! Hsh8 (talk) 15:23, 16 June 2009 (UTC)

Check out the Threshold of pain article stub. It needs references! I'm not next to my bookshelf right now but I am remembering that the threshold of pain is frequency dependent, such that very, very loud low frequencies aren't as painful as very, very loud mids. Also, temporary threshold shift can occur in listeners who have been in the presence of loud sound for a little while, so that the threshold of pain can shift up to 130 dB or so for that person. Temporary threshold shifts from 5 to 20 dB have been observed, but an average value of 10 dB is present in much of the literature. Anyway, 120 dB is indeed the starting point for un-shifted listeners to experience pain.