Seeing the sound to locate its source

Seeing the sound to locate its source. Several microphones arranged in a given pattern can be used to locate a sound source by analyzing the phase mismatches of the signal at different receivers. That long-established technique is called beamforming. The top panel of the figure shows the output from a line of 19 microphones in response to a simulated incident plane wave. The dark lane at 0° identifies the direction of the source as being broadside; that lane would shift up or down for a source in a different angular direction. The other dark lanes appearing at high frequencies are unavoidable artifacts—spatial aliasing—due to the discrete separations of a finite number of microphones. Those artifacts limit the technique to the lowest frequencies. If infinitely many microphones formed a continuous line, the artifacts would go away and a larger frequency range could be used. Researchers from the Danish Fundamental Metrology Institute...