Headphone simulation of free-field listening. I: Stimulus synthesis

TLDR

The study develops headphone‑presented stimulus synthesis methods that emulate free‑field ear‑canal waveforms. It measures each subject’s free‑field‑to‑eardrum and headphone‑to‑eardrum transfer functions across many source positions, builds digital filters from these measurements, and applies them to stimuli. Across ten subjects and 144 source positions, the resulting simulations match free‑field waveforms within a few dB in magnitude and a few degrees in phase up to 14 kHz, with error estimates consistent with prior literature.

Abstract

This article describes techniques used to synthesize headphone-presented stimuli that simulate the ear-canal waveforms produced by free-field sources. The stimulus synthesis techniques involve measurement of each subject's free-field-to-eardrum transfer functions for sources at a large number of locations in free field, and measurement of headphone-to-eardrum transfer functions with the subject wearing headphones. Digital filters are then constructed from the transfer function measurements, and stimuli are passed through these digital filters. Transfer function data from ten subjects and 144 source positions are described in this article, along with estimates of the various sources of error in the measurements. The free-field-to-eardrum transfer function data are consistent with comparable data reported elsewhere in the literature. A comparison of ear-canal waveforms produced by free-field sources with ear-canal waveforms produced by headphone-presented simulations shows that the simulations duplicate free-field waveforms within a few dB of magnitude and a few degrees of phase at frequencies up to 14 kHz.