I reckon you're wrong if as stated the insulation is really light in weight. There are two ways to control sound. Controlling vibration which would involve something stuck firmly to the surface of the metal (which it isn't) or sound blocking which require a sheet of material with mass. If it is light like a thick fabric, then it is certain to be thermal control primarily.
This is why actually you are better off binning the jute insulation inside the car and replacing it with more modern materials as it simply isn't dense enough to be an effective soundproofing material.. Modern materials also don't hold water and stink when wet.
This is why actually you are better off binning the jute insulation inside the car and replacing it with more modern materials as it simply isn't dense enough to be an effective soundproofing material.. Modern materials also don't hold water and stink when wet.