A new method to determine the frequency response of enclosures using masked tones

Existing methods for equalization of enclosures are traditionally carried out in an empty room due to the annoying effect of the signals employed (pink noise, 1/3 octave tones, etc.) over the audience. Under these conditions, the frequency response and the subsequent equalization are determined from results that do not take into account the presence of people nor any other change that may occur in the room while the musical event takes place. In addition, this kind of equalization cannot be objectively readjusted during the event. In this contribution, a method to determine the frequency response of enclosures in an imperceptible way for the audience is presented. It involves including a test signal within a musical track that, thanks to the behaviour of human hearing, can be masked and successfully recovered using reference microphones. Hence, it is possible to obtain the room transfer function in the presence of public and perform the equalization adjustments while the music track is being played. The results agree completely with traditional methods, the great advantage being the possibility of performing the equalization at any moment during the musical event and in a transparent fashion with respect to the audience.