Originally Posted by MarkS
What's wrong with this is that it implies that you're depending on your ears for what's happening behind you ... as if they were a substitute for a mirror. Will sound tell you that another biker, a hybrid car, an electric or someone who's engine has died on the downhill and is drifting is coming up behind you? Will sound give you accurate distance information? I don't think so.
In driver's ed they teach you check your mirrors every 10 seconds or oftener depending on circumstances. If this is true for cars, how much more so for bikes? There's a variety of mirror solutions for bikes available these days.
Except that driving with headphones is illegal in almost every state. Mirrors won't tell you a firetruck is coming through an intersection. Nor will they show you what's ahead. You don't use sound only for what's behind you.
When I lived in Seattle the thing that would scare the hell out of me when I was riding in the city was the trolley buses. They are almost silent. Every time one came up behind me I'd swerve. Would you want every car to be almost silent? I sure as hell don't.