NO ~ not hard to understand at all, because "music" is exactly what you're describing.

That big cargo deck behind you reZonates at various RPM, and acts exactly like a drumhead for road noise and exhaust note. It's been the subject of many articles since the '70s.

Well said, actually.

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1970 240Z

I actually have two S30s with Catalitic converters a 77 ZAAP and a 78 Black Pearl both California emissions cars factory fitted with Cats and Unleaded fuel restrictor in the Gas inlet and stickers on the gas lid and fuel gauge in the dash "Unleaded Fuel Only" They are both low mileage cars and have their original exhaust systems that are covered in finned shields including the muffler . Another cool feature in case the Catalitic converter gets to hot there is a light above the A/C Vents that says "FLOOR OVERHEAT"