Abstract: A helmet including an active noise cancellation (ANC) system which includes a first reference microphone for measuring sound pressure at a first location on a first side of the helmet, the first location between a defined spatial region and a first source of sound and a second reference microphone for measuring sound pressure at a second location, different to the first location, on the first side. The second location is between the defined spatial region and a second source of sound. A loud speaker is provided in or adjacent to the defined spatial region. A control unit determines, based on output signals from the first and second microphones, a drive signal for driving the loudspeaker to generate a sound signal that at least partially attenuates, in the defined spatial region and in the first frequency range, the sound signals from the first and second noise sources.

Abstract: A helmet including an active noise cancellation (ANC) system which includes a first reference microphone for measuring sound pressure at a first location on a first side of the helmet, the first location between a defined spatial region and a first source of sound and a second reference microphone for measuring sound pressure at a second location, different to the first location, on the first side. The second location is between the defined spatial region and a second source of sound. A loud speaker is provided in or adjacent to the defined spatial region. A control unit determines, based on output signals from the first and second microphones, a drive signal for driving the loudspeaker to generate a sound signal that at least partially attenuates, in the defined spatial region and in the first frequency range, the sound signals from the first and second noise sources.

Abstract: An active noise cancellation (ANC) system has a mounting plate, a first face of which is configured to be disposed against an inner surface of a helmet to form, with the helmet, a chamber. When the mounting plate is mounted on the helmet, a loudspeaker provided on the first face of the mounting plate is within the chamber. The plate has an aperture for allowing transmission of sound from the loudspeaker to the spatial region. At least one reference microphone is mounted on a second face of the plate. The plate acts as a mounting plate for components of the ANC system, simplifying the process of installing an ANC system. Also, the plate serves to define a chamber that accommodates the loudspeaker of the ANC system and provides good acoustic coupling of the sound signal from the loudspeaker of the ANC system into the quiet zone of the ANC system.