I don't think I go by engine noise at all anyway so I don't think there's any difference. Almost all the time I'm riding, it's on 50MPH + roads and the road/wind noise is the major factor there, so hybrids make as much noise as most cars. Occasionally there's a jacked pickup that is loud, but even then, it's mostly tire noise, not engine noise, that dominates.
I used to drive a Ford Probe that was so quiet that I'd scare joggers (yes, without music players) on quiet residential streets, so it's nothing new.
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Work: the 8 hours that separates bike rides.