Are low frequencies important for effective sound masking?
Leo Beranek and the expert staff at Bolt, Beranek and Newman reported the range of spectra found in typical offices from HVAC systems and activity noise in combination with early sound masking systems, as illustrated below. This spectrum has often mistakenly been taken as the optimal masking spectrum, and has remained a reference standard for decades. The pre-programmed Qt Quiet technology™ spectrum does lie within this band down to 200 Hz but is characterized by less low frequency energy below that frequency. Low frequencies contribute to subjective loudness but do not contribute to speech privacy and therefore are not required or desirable for effective sound masking.
