Active control of excessive sound emission on a mobile device.

During a phone conversation, loud vocal emission from the far-end to the near-end space can disturb nearby people. In this paper, the possibility of actively controlling such unwanted sound emission using a control source placed on the mobile device is investigated. Two different approaches are tested: Global control, minimizing the potential energy measured along a volumetric space surface, and local control, minimizing the squared sound pressure at a discrete point on the phone. From the test results, both approaches can reduce the unwanted sound emission by more than 6 dB in the frequency range up to 2 kHz.

A bank of beamformers implementing a constant-amplitude panning law.

This paper describes a technique for designing a collection of beamformers, a "beamformer bank," that approximately produces a constant-amplitude panning law. Useful in multichannel audio recording scenarios, a point source will appear with energy above a specified sidelobe level in at most two adjacent beams, and the sum of all beam signals will approximate the source signal. A design method is described in which a specified sidelobe level determines beamwidth as a function of arrival direction and frequency, leading directly to the number and placement of beams at each frequency. Simulation results are presented verifying the proposed technique's performance.