I've been seeing a bit of this type of article lately, perhaps due to the fuel prices rising, and have wondered; if this is true, why do I continue to hear exha

I've been seeing a bit of this type of article lately, perhaps due to the fuel prices rising, and have wondered; if this is true, why do I continue to hear exhaust noise when coasting in gear? Exhaust noise is purely the sound of detonation, which requires fuel. So why do I hear it if there is no fuel being used? I'm open to the possibility of my brain faking me out and I'm NOT actually hearing it, too. But I'm pretty sure I am. (NB: My car is a 1995 model, but it is fuel injected.)