Despite all the noise its electric buses will be able to make, the company promises they still won't be as loud as their gas-powered counterparts. Volvo Director Peter Danielsson said in a statement:

"The bus can be heard -- but without being disruptive. We've solved this problem by developing a synthetic background sound with a frequency range that is not perceived as disruptive. For instance, it does not penetrate windows with triple glazing, unlike the low-frequency noise made by a diesel engine."

The Swedish corporation will roll out its new detection system to its European fleet by 2017. You can watch a demo of how it works below, though, complete with samples of the vehicles' "non-disruptive" warning beeps.