The debate rages on about the sound, or rather the lack of sound, coming from electric vehicles. Their relative quietude could make roadside-housing rather more tenable in the future, but, if you ask some people, will turn those cars into silent killers. We've seen some crude noisemakers attempt to make those cars a bit less lethal, but that just brings us back to the noise pollution issue again. ECTunes has what sounds like a solution that will better appeal to both camps: directional sound. The prototype Citroen pictured above emits tones only audible to those right in its path, straight ahead when traveling forward and behind it when in reverse, silencing altogether at 30mph when wind and tire noise is enough of a deterrent to those who can't see oncoming traffic -- or who simply choose not to. A solid, reasonable solution to the problem? Absolutely. Will it make those on both sides of those topic agree? Unlikely.