Abstract
Objective: Light pulses transmitted through the external auditory canal are captured by a photodetector on a tympanic membrane contact transducer creating a current, which activates a micro-motor. The hypothesis that an extended bandwidth (10 kHz) contact transducer residing on the tympanic membrane will improve speech understanding in noise is tested.
Method: Reception thresholds of sentences (RTS) were measured with target speech at -45° and two talkers at +45°, simulating a photonic transducer on (1) normal and (2) hearing-impaired subjects. HINT sentences and masking speech materials were recorded at 24-kHz bandwidth and low-pass filtered at 4, 6, 8, and 10 kHz.
Results: For normal hearing subjects (n = 12), the mean RTS was -17.4, -19.1, -19.3, and -20.7 dB for 4, 6, 8, and 10 kHz respectively. For hearing impaired subjects (n = 12), the RTS unaided full bandwidth was -10.0 dB and -10.0, -11.9, -12.2, and -12.4 dB for aided 4, 6, 8, and 10 kHz respectively. The results indicate significant improvements of 3.3 dB (P < .001) in normal hearing and 2.4 dB (P = .02) for hearing impaired subjects for the 10 kHz vs the 4 kHz bandwidths. Initial measurements with the IDE-approved photonic hearing device are consistent with the simulation study.
Conclusion: The results suggest that acoustic cues above 4 kHz in a hearing device can greatly enhance the ability to hear target speech in noisy environments. This opens up possibilities for a unique hearing system using only light to transmit sound to vibrate the tympano-ossicular system.
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