Shock Response Spectra and dB's... 1

[mathlete7]

Hello,
I'm looking at defining some qualification shock response spectrum (SRS) levels for some hardware that is near a pyrotechnic device. I've seen that most specs recommend testing anywhere from +3dB to +6dB above the limit SRS levels for qualification of hardware. So my question is this:
When dealing with SRS (where the units are in G's) are the dB levels defined as 10*log(L2/L1) or 20*log(L2/L1)?

I know that when dealing with power spectral density levels you have:
10*log(L2rms^2/L1rms^2) = 20*log(L2rms/L1rms)

However since the units for an SRS aren't rms values I'm not sure if I should be using a factor of 10 or 20 to define decibel levels.

Thanks!

 

[GregLocock]

With dBs you use 10 log if the units are a measure of power or energy (W, J, (ft lb)^2), and 20 log if it is a measure of something that needs to be squared to get to an energy related measurement.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.