Anyone who has spent any time driving a Land Rover (new or old), knows they are not the quietest of vehicles to drive. Engine and transmission noise is always present. Sound proofing on modern Landies is functional but on the older Series vehicles is practically non existent… (but was offered as an optional extra)
To provide some sound attenuation between the engine bay and the cab, I’ve used Dynamat. My 110 Defender Hard Top also received the same treatment when I bought it and it transformed the driving experience.
Dynamat adds mass to sheet metal panels. For example…. If you’ve ever seen the underside of an old bath or kitchen sink, you will have seen an adhesive sheet (about 20 x 20 cm) under the area where the water hits the surface…. same principal… adding mass to the panel to reduce reverbertion.