Noise reduction arrangement including: a plurality of actuators (3(n))
for generating secondary noise (ps) to reduce primary noise (pp)
and being located in a first surface; a plurality of errors sensors (2(m))
located in a second surface parallel to the first surface for sensing a total amount
of noise resulting from the primary noise after being reduced by the secondary
noise; a plurality of control elements (5(i)) for controlling the
actuators (3(n)) based on the sensor outputs, wherein the distance
(d) between the first and second surfaces is such that reduction in power RP of
the total amount of noise relative to the primary noise within a predetermined
frequency band is within the following range: 0.9RPmaxRPRPmax
in which RPmax is the maximum obtainable reduction in power of the total
amount of noise relative to the primary noise, both RP and RPmax being
expressed in decibel.
