Abstract: An audible signaling device uses one or more digital signal processors to modify the shape of a sound field to put high sound pressure levels only in a predetermined pattern, thus minimizing undesirable high volume levels in adjacent areas. Using digital signal processing techniques, and a plurality of high power amplifiers and loudspeakers mounted in an array on a moving vehicle, a carefully engineered sound field can be produced. The shape of this sound field is controlled by the frequencies amplitudes, and phases of the signals, as well as the characteristics and placements of the speakers in the array.

Abstract: A system and method that provides a party that has been placed on hold control of music on hold. A dual-tone, multifrequency (DTMF) detector and a processor in the music on hold system monitor two-way connection. If a predefined DTMF signal is detected, the DTMF detector notifies the processor to disable the music on hold. Further, a DTMF code may be defined to cause the processor to decrease/increase the volume of the music on hold.