Method for inspecting the emission of an audio safety message in a vehicle

A method for monitoring the transmission of a safety audio message via at least one loudspeaker located onboard a vehicle to the occupants of the passenger compartment of said vehicle, said safety audio message having a predetermined duration, said loudspeaker having a maximum frequency, said method comprising:

• transmitting an audio signal comprising the safety audio message and, mixed with said safety audio message, an identification signal comprising an identification digital audio message that is looped and frequency modulated, said identification signal having a frequency comprised between 20 kHz and a frequency ceiling lower than a maximum frequency of said loudspeaker, the identification digital audio message comprising a unique identifier associated with said safety audio message,
• recording an ambient sound in the passenger compartment by a microphone,
• filtering the recorded signal by a bandpass filter, so as to obtain a filtered signal having frequencies comprised between 20 kHz and a frequency ceiling,
• demodulating the filtered signal so as to reconstruct the identification signal comprising the looped identification digital audio message,
• analyzing the reconstructed identification signal to determine:
• whether the unique identifier corresponding to the transmitted safety audio message is found therein, and
• by counting a number of occurrences of the identification digital audio message in said reconstructed identification signal, whether the time for which the identification signal was transmitted without interruption is indeed equal to the predetermined duration of the safety audio signal, and
• determining that the safety audio message has or has not been correctly transmitted in the safety audio message's entirety depending on the analyzing step.