In a early Lotus Elise of the first series, you hear everything.
Can make you nervous after a big rebuild or power increase.
You can literally hear the injectors ticking at idle from the driver seat.
There is virtually no sound insulation, aluminium tub chassis, open top, mid engined. The "firewall" consists of a 3mm thick glass fibre sheet and you sit right in front of the engine for a RHD car and gain some extra 30cm distance in a LHD car. Seat mounts are short, seat padding is pretty thin, engine is partly mounted to the same alloy tub as the seat.
The engine/boot lid has big grilles to let the air out though the top. Noise also passes well. The lid is made from thin aluminium sheet and has no insulation material attached. High frequency noise easily exits the engine bay.
With a hard top or soft top fitted the cabin noise actually gets louder.
I have a radio installed, but past city speed it becomes pretty much useless. This is with a quiet muffler with its valve closed.
https://youtu.be/h-898etjgx0