Personal active noise cancellation method and device having invariant impulse response

A personal method for active acoustic attenuation comprising the following stages:

• a) a source (30) is provided that is suitable to deliver an active attenuation signal (SA) in order to reduce an unwanted noise in response to a received control signal,
• b) sensor means (20) are provided for picking up the unwanted noise,
• c) an acoustic structure (2) is provided that is suitable to support the source (30) as well as the sensor means (20) in proximity to the head of an individual,
• d) electronic control means (50) are provided that are suitable to generate the active attenuation control signal for the source,
• e) a selected electrical signal is applied beforehand to the input of the source in order to determine at least the impulse response (H), during a predetermined period, between the output of the source and the input of the sensor means, and
• f) in real time the active acoustic attenuation control signal is determined in accordance with a predetermined processing rule that is established at least in accordance with the impulse response as determined previously, in order to minimize the energy of the signal delivered by the sensor means,
• wherein stage c) consists in converting said acoustic structure (2) while maintaining means of support and protection (520, 600), delimiting a volume (564) where the sensor means (20) and the source (30) are accommodated, said volume being maintained invariant, at least during the determination of the active attenuation control signal and in the presence of the individual, permitting the impulse response (H) between the output of the source (30) and the input of the sensor means (20) to be maintained invariant.