| Summary: | 碩士 === 朝陽科技大學 === 資訊與通訊系碩士班 === 101 === Sound recognition utilizes sound signal characteristics to obtain meanings encompassed in the sound information. Study of sound focuses mostly on the tempo of human language or music but little on the recognition of ambulance siren which is critical to the safety of life. The function of an ambulance siren is to remind other drivers on the road to make timely response to give way to the ambulance. However, the siren of an ambulance is often disrupted by noise and blocked by voices in a real life situation. This prohibits other drivers from hearing the siren. This research presents a method to recognition ambulance siren. Upon the detection of an ambulance sound, it can be utilized to verify if the sound signal is from an ambulance siren and then to remind drivers in a timely way that an ambulance is approaching.
The National Fire Agency has specific regulation on the frequency and duration on ambulance siren. This regulation defines high frequency of between 900 Hz to 1000Hz and low frequency of between 650Hz and 750Hz with 0.6 second duration for high frequency and 0.4 second duration for low frequency. The sound of siren is composed of regular alternating sound between high and low frequencies. Based on this frequency characteristic, this research utilizes the Longest Common Subsequence (LCS) algorithm. With LCS output statistics, it further uses fuzzy judgment method to verify if ambulance siren exists in the sound signal. Our experiment result indicates that, under environments with different noises, the average true positive rate is 92.8% when the system detects ambulance sound and 99.8% when the system doesn''t detect ambulance sound.
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