We aim to introduce to the hearing-assistive device industry the first commercialized microphone that combines all three axes of acoustic pressure gradient onto a single silicon chip. We expect the technology to empower the signal-processing community with a new tool which, when used in conjunction with a conventional omnidirectional microphone, will facilitate new features like ultra-sharp directionality adaptable in real-time by the user and/or artificial intelligence algorithms which scan for desired inputs while filtering out unwanted noise. Directional sensing and the ability to filter out undesirable background acoustic noise are important for those with hearing impairments. Hearing impairment is associated with a loss of fidelity to quiet sounds, while the threshold of pain remains the same. As such, hearing impairment causes a loss of dynamic range or "window" of detectable sound amplitudes. Directional sensing enables preferentially amplifying desired sounds without amplifying background noise. As the first step, we aim to accelerate the commercialization of recently introduced biologically- inspired "rocking" style microphones by synthesizing these designs with integrated, robust piezoelectric readout which is ideal for addressing the low-power, small-size, and high levels of integration required of the hearing-aid industry. Previous work in this field using laboratory prototypes and optical readout have demonstrated the merits of the biologically-inspired sensing approach (i.e. a simultaneous 20-dB SNR improvement and 10x reduction size improvement beyond what is achievable with present-day hearing-aid or MEMS microphones). By synthesizing a piezoelectric embodiment as an alternative to optical readout, we aim to accelerate through many of the commercialization challenges so that an impact to the hearing device industry can be made. Further, the proposed readout is better adapted towards integrating multiple microphones in the same silicon chip. In Phase II, we aim to integrate a microphone with both in-plane axis of directivity with an out-of-plane directional design to form a complete 3-axis pressure gradient sensor.
Studies show that today 2% of Americans wear a hearing aid, whereas at least 10% of Americans could benefit from a hearing assistive device. The major reason for this gap is patient dissatisfaction. Hearing-aid wearers suffer from what is known as the cocktail party effect. When the gain is turned up to hear the person speaking across from you, noises in the background are equally amplified - making every scenario sound like a cocktail party. This research aims to make a positive, long-term improvement to hearing-aid patient satisfaction by making commercially available directional microphones with high fidelity.
|Kim, Donghwan; Kuntzman, Michael L; Hall, Neal A (2014) A transmission-line model of back-cavity dynamics for in-plane pressure-differential microphones. J Acoust Soc Am 136:2544-53|