Spectral Correction of Audio Objects in Stereophonic Rendering

This paper presents a comprehensive model for ear-signal level coloration in stereo amplitude panning, enabling the calculation of monaural correction filters that equalize the average coloration over a small area around the sweet spot. The model takes into account the speaker setup geometry, listener Head-Related Transfer-Functions (HRTFs), the employed pan-law, the direct-to-reflected sound ratio, and the correlation between the speaker signals at the listening position. Coloration in diffuse sound reproduction is also investigated. The coloration model is validated using binaural room impulse response measurements, and the correction filters are found to effectively reduce the difference in composite ear power spectrum between a discrete and virtual center source. A listening test on the perceived spectral difference between these two cases, with stereo setups in front of and behind the listener, indicate that the correction filter improves timbral similarity between a virtual and discrete center source for rear speaker panning. The test also indicates that remaining unmodeled coloration sources are large, especially for front panning. However, a second listening test finds that the correction filter improves accuracy of perceived direction in front panning by mitigating the phantom image elevation effect.