The effect of microphone placement on localization accuracy with electronic pass-through earplugs

Many audio applications make use of electronic pass-through listening devices that intercept the signals entering a listener's ears and electronically process them in real time. An important issue in designing such devices is ensuring that they maintain the listener's natural ability to localize sound sources. Previous research suggests that optimal localization requires a completely-in-the-canal (CIC) design with a system bandwidth of at least 13 kHz. However, most practical designs have to make engineering compromises in terms of bandwidth and/or microphone placement that cause some degradation in localization performance. The paper compares open-ear localization to localization with seven different pass-through devices: five custom-molded earplugs with different microphone configurations; a CIC hearing aid; an electronic earmuff. The results show that earplugs interfere substantially less with localization than earmuffs, but that the frequency response has a larger impact on performance than does physical configuration in earplug systems that are bandlimited to frequencies below 6 kHz.