[Merv and Sharon]

I was struggling with my 20-years ago audiological training there! Steven is right and 3dB is the doubling-sound power difference, not 5dB.

However, it is interesting that they use dBA (filtered to somewhat replicate human hearing; and is less sensitive under 1000 Hz) rather than dBC which is a more flat response. I would be interested to know where in the sound spectrum the Cobra exhaust/s is/are most prominent. That could also influence how we try to attenuate the noise sources. I suspect that there is a good deal of low frequency noise there. Different strategies could be applied for attenuating higher and lower frequencies. It is also good to see that they use a standard set up for the measurement. I am still wondering if they use the average measurement of output over several trials or only record the 'peak' or most intense point? Obviously with cars being so close to the limit an average is an advantage.

Last, the exhaust guy I spoke to at the Gold Coast yesterday, who does lots of Cobras, said that he always fits plates to restrict sound output for registration. I am interested to see what he does.