dynamat. works well, big job. it works by adhering a tar based sheeting to steel and plastic, to reduce vibration of that particular part, which reduces sound waves from the panel flexing.
to do it properly, you stick it to every panel, especially every large panel, including roof and spare wheel well... then for something extra you put it on the reverse side of trim panels too. the thicker it is, the heavier it is, the better it will work.
the cavities between these also tend to amplify noise like a sub box, so in the boot i like to pack quilt wadding behind the trim
the weakest link in cars however is the glass. tyre noise will pass thru that regardless...