In reply to bdscott, that Channel 5 presenter is an irritating bufoon and I wouldn’t take much notice of what he has to say. I think a more respected source is The Inside Line website at:
http://www.edmunds.com/insideline/do/Dr ... eId=116621which states that
“One measure that did show a difference was interior sound levels. That soft top registered 77.0 decibels at 70 mph; the new PRHT, just 72.9. That's a big change, one we especially appreciated in the final hours of a freeway haul back to Los Angeles from the Monterey Historic Automobile Racesâ€. This confirms similar figures I have seen.
Not sure exactly what 70 mph is but I guess it is about 110kph.
Four dB is a big difference because dB is on a logarithmic scale so that difference is easly detected by the human ear but the problem is that decibel meters measure the intensity of noise levels, not the loudness which is what we subjectively ‘hear’. What is objectional at a particular frequency to one person’s ear may be acceptable to another. Therefore an objective measures of sound intensity such as decibels should not be confused with loudness, a subjective measure. Unfortunately, loudness cannot be measured I understand, because is also affected by intensity, frequency and duration.
I guess this is why most road tests reviewers don’t provide dB readings with their reviews.
Another problem with the reporting of dB readings in car reviews is that the reviewers never say on what type of road surface they are travelling. There is an amazing difference between suburban streets and freeways and semi-rural and country roads.
Sorry about turning this distinguished forum into a physics lesson
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The jaycar stuff is not much cheaper but more of a hassle to install as you have to use spray adhesive or contact cement. Dynamat is self adhesive, and very easy to use. I've installed it in the doors of my car to improve the sound of the stereo by reducing panel vibration, which creates a surprising amount of noise.
