Maybe? It doesn't have a scale on the vertical, so you don't know how loud it is. It only shows that the horizontal bars are about 10dB. It's not a good chart. Essentially, somewhere just below 220Hz, it appear that there is a 10db dampening of the noise. We still don't know what that dampened level is though which makes this a meh chart at best
Since sound levels differ with distance and environment, absolute levels are not all that meaningful without a detailed explanation of their measurement setup. A 10dB reduction roughly corresponds to something sounding about half as loud to human perception.
I can see this point, but a 10db reduction from 90db to 80db is still really loud. A 10db reduction from 40db is even more impressive.
So having some baseline would still be helpful just to get some sort of reference. For science, you'd put the dampened wheels on a car and get readings from inside the car as that's the only thing relevant. You'd then replace the wheels with non-dampened versions on the exact same car, and then take your measurements from inside the car again.
This isn't rocket science. It doesn't need to be any more complicated than taking readings where your target audience will be sitting. The fact that this even needs to be stated explicitly just makes me sad for common sense
