| 摘要 |
PURPOSE:To detect securely whether a vehicle is in a tunnel or not without reference to the circumferential condition of the vehicle by extracting a component corresponding to a reflected sound which returns from the internal wall of the tunnel by using cepstrum, and comparing it with a reference value. CONSTITUTION:A sound information signal inputted by a microphone 1 is processed by an amplifier 13, rectifying part 15, and A/D converter 16 and the microcomputer 17 uses the processing signal to decide whether the vehicle is in the tunnel or not. When it is judged that the vehicle is in the tunnel, the actuator for internal/external air switching of a vehicle air conditioning device is driven. The microphone 1 is provided to input a reflected sound from the internal wall of the tunnel, specially, in the tunnel, not to mention an ambient sound of the vehicle, and this is fitted outside of the vehicle by being incorporated in, for example, a fender mirror. Consequently, the detection precision is improved as compared with when a noise level outside the vehicle is used, and the detection is secured regardless of the circumferential condition of the vehicle. |
