Top Speed Axle-Back exhaust db measurements

[pantdino]

I just installed a Top Speed axle-back muffler on my otherwise totally stock '13 FRS.

I used the SPLnFFT db meter download on my iphone and recorded db inside the car sitting still with windows up at idle, 2000 rpm, and 3500 rpm. Also recorded were the sound behind the car at idle, the inside at 63mph at steady speed, and max db at full throttle in first gear from a slowly rolling start.

In short, all the numbers with the car sitting still were 2-3db greater with the TS muffler. There was no change in the noise at 63mph because it is mainly tire noise you hear then, and there is no droan at all.

The main change is a deeper sound which is only present during acceleration. The max db inside was 83db with the windows up and 84db with them down, although I didn't do enough runs for those last 2 figures to be 100 reliable.

I am happy with the sound and loudness level. With the stock exhaust the car sounds like a family sedan and this is much more in keeping with it's character.

For $400 with new nuts, bolts, and gasket I recommend it.

[pantdino]

For those of you who don't know, a 2.5 - 3db increase represents twice the sound energy. So like you have one violin or speaker playing and another starts playing at the same loudness.

[churchx]

+3 dB is doubling sound intensity (acoustic energy).
+10 dB is twice perceived volume (in other words - twice as loud by human hearing/sensed psychoacoustics).

So 80 dB is twice louder then 70 dB, end so is 100 dB vs 90 dB. Pitty that logarithmic scale numbers are way less intuitive then linear scale, and may bring "suprises" in eg. judging how loud exhaust might be purely by posted numbers, and underestimating difference for example between 85dB vs 93dB, intuitively judging those numbers to be of lesser difference then they really are like if eg. temperature of 85C vs 93C or distance of 85m vs 93m.

Nice paper on this.
+10 dB = x2 sensed
+6 dB = x1.516
+3 dB = x1.232