Electric and hydrogen cars: What noise should they make?
17 May 2011 Last updated at 06:09 BST
What sound should electric and hydrogen fuel cars make in the future ?
It is a unique and slightly bizarre question facing the car industry, as most electric vehicles are virtually silent. This can cause problems for other road users.
The answer could have a huge impact on our lives by transforming how our towns and cities sound in 10 or 20 years' time.
Researchers from Warwick University are looking into the issue by testing out a range of alternative vehicle sounds.