resonate frequency a vehicle

I saw someone state this in a post in the comp sub topic. i was wondering how do you find this frequency and if someone could explain a little more what it means.

Thanks

Without access to an anechoic chamber and many sophisticated pieces of test equipment you will probably not be able to determine this.  However, many auto manufacturers do determine their vehicles resonant frequency and often all you have to do is ask.

What it means, in general, is the frequency at which the structural elements of the vehicle vibrate in resonance.  Manufacturers want this number to be as low as possible so that the vehicle does not develop annoying rumbles at highway speeds.

Maybe we're talking about two different things.  A vehicle's "resonate frequency" is a function of the materials, construction, suspension, welding quality, etc. and is like the Fs of a loudspeaker: it is the point where the system inherently tends to vibrate most readily.  For most cars and trucks on the road, this number is down around 5 to 12 Hz - way below human hearing and not too useful for competition of any sort.  Determining it is a very involved process and is way beyond the means of most car audio shops.  But perhaps what you really mean is the frequency where the car exhibits the most cabin gain.  This is a function of the interior materials and the vehicle's physical spaces and shapes, and is the frequency most "boosted" by the natural physics inside the vehicle.  This is usually around 50-80 Hz and could be very useful to know for competitions.  It can be fairly easily determined using an RTA.

Is this what you mean?

Real Time Analyzer.  A piece of test equipment.  Here's one use for them.