With the advent of technological advancement cars are becoming more and more silent, that is the car engines produces very low sound when compared to the earlier car engines. On the other side the electric cars and the hybrid cars which runs on electric power not only saves fuel and reduces pollution but also runs very quietly. But this has become a problem for the pedestrians walking on the road and cyclist. They find it difficult to hear where the car approaches from. The solution to the problem has come with the external sound system to fit in front and rear of the electric and hybrid cars. American congress is passing a bill to establish a minimum level of sound for the vehicles that run on electric power, so that the pedestrians and the blind can hear their coming. Recent studies found that people are less accurate when judging the electric cars approaching them. Electric cars produce audible sound at the speed thirty miles per hour, which is too possible because of the air flow through the car body not from the engine. The external speaker attached with the cars is enough to produce the sound that makes the people to judge the oncoming vehicle. The synthesized noise could help in reducing the noise pollution. Unlike the car engines the speaker attached produces sound which is highly directional. So people working in office can have the relief from the noise radiated from the internal combustion engine.
