Using individually equalized playback of binaural recordings from an electronic orchestra to determine the effects of early reflections on proximity, localization, and loudness

Abstract

Reflections in the first 50 ms are often assumed to enhance sound quality, but data supporting the assumption are lacking. We need to know when reflections are beneficial, and when they are not. Work by Lokki et al. may help to answer this question, but we have developed a binaural recording and playback technique that yields as good or better results. The key is individual equalization from the microphone to the eardrum of a listener. We have developed a quick and non-invasive method of headphone equalization that produces accurate timbre and frontal localization without head-tracking. This enables binaural impulse responses from a number of instrument positions in real halls to be manipulated by adding or deleting individual reflections and then evaluated with blind listening tests. Data from Boston Symphony show that early lateral reflections in the front of the hall are typically inaudible, but early medial and lateral reflections in the rear of the hall can reduce or eliminate proximity, clarity, impact, envelopment, and the ability to localize individual instruments. Deleting one or two of the earliest and strongest reflections improves all of those perceptions with no effect on loudness.