Sound Source Localization via Cockpit Voice Recorder

The Flight Data Recorder (FDR) and the Cockpit Voice Recorder (CVR) both can strongly facilitate the investigation of aviation accident. Besides the pilot communications, the CVR can also record the non-speech acoustic information as the sound of propeller and the voice of control levers and switches. For this reason, the CVR can provide the last operations of pilots in the accident and assist the investigation. The first step to locate sound sources of switches in traditional method is calculating the time-delay of arrival (TDOA) which is caused by different propagation length form the sound source to different microphones, and the second step is locating the position of sound sources with calculated TDOA. Furthermore, we can introduce the character that the allocations of switches are identical in the same type of aircraft, and premise that the relative positions of three cockpit microphones do not alter substantially. Under the premise, the task of sound source localization in the cockpit could be simplified to a simple table lookup issue, while the table consists of the TDOA set and each corresponding switch. Besides, the other method of hyperbolic positioning via trilateration is introduced. Trilateration is applied to obtain the intersection of hyperboloids which are from the estimated TDOA. Combine this hyperbolic curve and the geometry of aircraft cockpit, and the sound source can be identified. At last, the performances and their pros and cons of these two methods are compared and verified with experiments.