Free speech unit e.g. for motor vehicle, has microphone on seat belt and placed across chest of passenger and second microphone and sampling unit selected according to given criteria from signal of microphone

摘要

The free speech mechanism has a microphone (18a-c), which is located on a belt (10) of a seat belt system which is placed across the chest or shoulder of a passenger. A second microphone (19) and a sampling unit (20) are selected according to given criteria from the signal of the microphone and produces an output signal. In the normal condition the signal of the first microphone (18a-c) is selected, and the second microphone (19) is stationarily arranged in the vehicle and that the given criteria are noise of a normal condition. The sampling unit compares the signals of the first and second microphone with one another and diagnoses noise if the signal of the first microphone is worse than the signal of the second microphone.