Active low-frequency modal noise cancellation for room acoustics: an experimental study

Low frequency background noise in rooms generated by numbers of human activities - traf-fic, railway, airport and industrial noise - creates major disturbances from loss of speech in-telligibility to stress and fatigue. To overcome such situations classical solutions generally consist in deploying resonator-like absorbing materials to reduce both the acoustic level and the reverberation time. Unfortunately these traditional acoustic treatments are not efficient enough to attain A-weighted level specifications imposed by regulation laws. In the context of cancellation of low frequencies in rooms, an experiment was performed to qualify and quantify performances of a low-frequency noise cancellation active system. So as to minim-ize and increase performance in noise reduction, active solutions are actually studied to attain and fulfill high expectations in terms of integration with high efficiency in opposite to pas-sive solutions. We propose an experiment based on active sources to counteract modal low frequency noise for quasi-stationary to permanent noise emission. We present some results using a step-by-step approach to understand the global behavior of the room excited in the frequency band of its first modes. Through coherent assumptions and observations we show the efficiency of low-power active system with a priori constraints affecting modal active control.