A Microphone-Array-Based System for Restoring Sound Localization with Occluded Ears

Abstract

Current helmets and hearing protectors interfere with the sound transmission to the ears and therefore affect the perception and localization of speech and other useful sounds. This is can be a serious drawback especially when the person wearing the protection has to operate in complex, unpredictable environments. A novel electro-acoustic system for sound pass-through was developed that can make hearing protection acoustically ‘transparent’. By using external microphone arrays tuned to have a directional sensitivity similar to that of the open ears, the system can not only improve audibility of lowlevel sounds but also restore normal sound localization. The tuning was done by selecting specific microphone positions and by designing digital filters through which the individual microphone signals are passed. The system was evaluated in a sound localization experiment. Two versions were tested: one with individualized digital filters and one with universal (generic) filters. A comparison was made with a system with single external microphones, and with an earmuff with no sound pass-through. An open-ear condition was included as reference. Results show that, across all occluded-ear conditions, localization performance is best for the microphone-array system with individualized digital filters. Compared to listening through passive earmuffs, the percentage of confusions (quadrant errors) i s nearly halved. However, localization performance is still not as good as with open ears.