Median-plane sound localization as a function of the number of spectral channels using a channel vocoder
A set of DTFs in the median plane for a typical listener. Panel (a) shows the measured DTF. Panel (b) shows the amplitude spectra of the same DTF for 0° azimuth and 0° elevation (solid thin line) and processed by the GET vocoder (vertical lines) for different numbers of channels . Channel corner frequencies are marked by the triangles.
Processing scheme for the GET vocoder. DTF information is bandpass filtered (BP filter) into channels, where the energy is measured. Gaussian envelopes modulate a sine tone, are replicated, and delayed (Rep) to make a GET train. The GET trains are energy normalized, weighted by the energy from a channel of the DTF, and summed. After temporal windowing, the result is the GET-vocoded signal.
Results of experiment 1. The upper panels show the individual data. The lower panels show the listener average and standard deviation. The left column shows the local polar error in degrees as a function of the number of channels. The right column shows the percentage of quadrant errors. Results for the WB clicks (CL) and WB noises (NS) are also included. The dashed lines show chance performance. The shaded area shows the average (solid line) and standard deviation (dotted lines) of the results from Middlebrooks (1999b) for virtual WB noise stimuli.
Results of experiment 2 averaged over listeners. Error bars show one standard deviation of the mean. The dashed lines show chance performance. Listeners were trained to all conditions before testing. Data from the WB noise and WB click conditions are repeated from experiment 1.
Results of experiment 3 averaged over listeners, the percentage of correct words for two spacings, and two SNRs in a speech understanding test. Error bars show one standard deviation of the mean.
Stimulus information for the spacings used in experiment 2.
Experiment 2: -values for differences between conditions. Significant -values (at the 0.05 level) are in bold.
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