Abstract: A method and apparatus for identifying an unidentified sound source in a 3-dimensional sensor array calculates a position vector for each of a plurality of sensors in the array. A time Fourier transform is computed based on time samples from each of the sensors. A spatial Fourier transform is computed for the results of the time Fourier transform and in part on the position vectors calculated. All three dimensional components of the wavenumber of the received signal, kx, ky and kz are explicitly calculated to generate spatial frequency information in all three dimensions. Direction of arrival of the received sound signal is determined in all three spatial directions providing unambiguous target localization and acoustic signature characterization.

Abstract: A non-vented shell earplug for insertion into the ear canal has multiple chambers configured as coupled acoustic resonators. Each chamber is provided with an acoustic element having inertia and resistance coupling the chamber to its neighbor to form multiple resonant chambers. The dimensions of the individual acoustic elements set the frequency response of the earplug, and determine the attenuation characteristics of the resonators. Unlike the single chamber resonator of the prior art, the multiple-resonator earplug provides attenuation in both low and high frequency segments of the noise spectrum. Additionally, the present invention teaches placing loudspeaker and/or sound sensing transducer for sound communication purposes and active noise control within the earplug, with their sound field patterns directed into a chamber for coupling to the ear canal. The use of multiple resonators enhances the high frequency communications response of the earplug.