| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an ambient condition monitoring device which can surely judge the kinds of other vehicles present nearby. SOLUTION: An acous to-electricity converter 1 is used to collect sounds around a vehicle and convert them into electric signals, and the required frequency components are extracted (band-pass filter 2) and are subjected to high- speed Fourier transformation (high-speed Fourier transformation part 3) to obtain a sound pressure level signal for every predetermined frequency. The frequency of time during which an average sound pressure level obtained through the averaging of the sound pressure level signals exceeds a predetermined level is calculated, and if the number of frequencies at which the frequency of time exceeds a predetermined value exceeds a predetermined number, another vehicle is judged to be present nearby. Based on the number of frequencies at which the frequency of time exceeds the predetermined value, the kind of the vehicle is judged.</p> |
