A helmet comprising a multichannel feed-forward active noise cancellation system for attenuating sound pressure in a first frequency range in a defined spatial region at a first side of the helmet, the ANC system comprising: a first reference microphone for measuring the sound pressure at a first location on the first side of the helmet, the first location between the defined spatial region and a first source of sound and being near the first source of sound; a second reference microphone for measuring the sound pressure at a second location on the first side of the helmet, the second location different to the first location, the second location between the defined spatial region and a second source of sound (1A,1B) and being near the second source of sound; a loud speaker in or adjacent to the defined spatial region; and a control unit for determining, 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 sources of sound (1A,1B, 1C); characterized in that a neck opening of the helmet represents the first source of sound, the defined spatial region is adiacent an ear of a user of the helmet, and the first location at which the first reference microphone measures the sound pressure is closer to the neck opening than to the defined spatial region; or in that a side of a visor of the helmet represents the second source of sound, the defined spatial region is adjacent an ear of a user of the helmet, and the second location at which the second microphone measures the sound pressure is closer to the side of the visor than to the defined spatial region. a first reference microphone for measuring the sound pressure at a first location on the first side of the helmet, the first location between the defined spatial region and a first source of sound and being near the first source of sound; a second reference microphone for measuring the sound pressure at a second location on the first side of the helmet, the second location different to the first location, the second location between the defined spatial region and a second source of sound (1A,1B) and being near the second source of sound; a loud speaker in or adjacent to the defined spatial region; and a control unit for determining, 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 sources of sound (1A,1B, 1C); characterized in that a neck opening of the helmet represents the first source of sound, the defined spatial region is adiacent an ear of a user of the helmet, and the first location at which the first reference microphone measures the sound pressure is closer to the neck opening than to the defined spatial region; or in that a side of a visor of the helmet represents the second source of sound, the defined spatial region is adjacent an ear of a user of the helmet, and the second location at which the second microphone measures the sound pressure is closer to the side of the visor than to the defined spatial region.