A low cost, non-individualized surround sound system based upon head related transfer functions: An ergonomics study and prototype development

This paper reports on the types and magnitudes of localization errors of simulated binaural direction cues generated using non-individualized, head-related transfer functions (HRTFs) with different levels of complexity. Four levels of complexity, as represented by the number of non-zero coefficients of the associated HRTF filters (128, 64, 32, 18 non-zero coefficients), were studied. Experiment 1 collected 1728 data runs that were exhaustive combinations of the four levels of complexity, nine simulated directions of sound (no direction (i.e., diotical-mono), 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° azimuth angles at 0° elevation), two repetitions, and 24 participants). Binaural cues generated from HRTFs of reduced complexity (from 128 to 18 non-zero coefficients) produced significantly higher localization errors for the directions of 45°, 135°, 225°, and 315° azimuth angles (p<0.01p<0.01). From the directions of 0°, 90°, and 270° azimuth angles, the cues produced by HRTFs with reduced complexity did not affect the localization error (p>0.2)(p>0.2). Surprisingly, cues produced by HRTFs of 128 non-zero coefficients did not have the lowest number of errors. From 45°, 135°, 225°, and 315°, the lowest numbers of errors were obtained from cues produced by HRTFs of 64, 32, 32, and 64 non-zero coefficients, respectively. Based on these findings, a prototype virtual headphone-based surround-sound (VHSS) system was developed. A double-blind usability experiment with 32 participants indicated that the prototype VHSS system received significantly better surround-sound ratings than did a DolbyTM stereo system (p<0.02)(p<0.02). This paper reports results from an original ergonomics study and the application of these results to the design of a consumer product.