passive means for at least one of absorbing and reflecting sound within an environmental space and active means for transforming said sound by building harmonic elements on said sound adjusted to provide masking sound;

the passive means comprising a partitioning screen for producing a discontinuity in a sound conducting medium in the environmental space;

the active means comprising:

means for receiving acoustic energy representing sound from the environmental space and for converting the acoustic energy into an electrical input signal;

means for receiving and analyzing the input signal into a plurality of frequency bands to derive control parameters;

a series of bandpass filters for receiving and filtering the input signal for generating an output, said bandpass filters corresponding in number to the plurality of frequency bands and having center frequencies in a harmonic relation to one another,

wherein the control parameters from the means are arranged to set automatically in real time the gain and the steepness of each filter in the series of filters in order to adjust the filtering of each said filter and control the output according to the level and quality of sound within the environmental space, and wherein the thus controlled series of filters are arranged to transform the frequency characteristics of the input signal by building harmonic elements on the received acoustic energy to provide masking sound;

means responsive to the output from the series of filters for generating an electrical output signal; and

output means for converting the output signal into masking sound for modifying sound within the environmental space.