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.