Revolutionary bike 'too quiet'

The problem with the "fuel cell" bike, which produces no polluting
emissions, is that it is too quiet.
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...with a noise emission equivalent to an everyday home computer,
motorcycle enthusiasts thought the "exhilaration" factor was missing.
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Concerns were raised that the motorcycle was too silent and might not
be noticed by other traffic and pedestrians.
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Harry Bradbury, chief executive of the bike's British manufacturers
Intelligent Energy, said: "What we are doing is introducing
flexibility into it, so that you can have ambient noise that is
tolerable - low-level noise sufficient for safety reasons - but which
can be switched off when desired."

http://news.bbc.co.uk/2/hi/europe/4353853.stm