Creare is actively developing technologies to enable hearing evaluation in noisy environments (such as for astronauts on the International Space Station). Some of these technologies are likely to have future application in industrial and commercial settings.

Hearing Evaluation Technology

Current audiological screening systems require noise-controlled facilities which limit their use in important applications, such as on the International Space Station and Space Shuttle; screening newborns and infants in the clinic; or patients of any age in other locations without access to sound-treated rooms. To overcome the limitations of current devices, we are developing acoustic signal processing algorithms, acoustic hardware, electronic hardware, and software to implement real-time, adaptive noise cancellation in conjunction with standard hearing evaluation tests. Our innovative hearing evaluation system combines a unique feedforward, adaptive, noise-cancellation algorithm with customized Distortion Product Otoacoustic Emissions (DPOAE) test protocols to reduce the background noise in the frequency ranges specific to the tests. By reducing the background noise levels around the test frequencies and customizing the testing protocols, our system enables higher signal-to-noise ratio (SNR) DPOAE measurement. The increased SNR will result in the ability to obtain DPOAE measurements for hearing evaluation and screening in relatively high noise environments such as on the Space Station and Shuttle, in newborn intensive care facilities, offices of pediatricians, schools without special audiology facilities, field hospitals, and remote or mobile clinics.

DPOAE hearing assessment consists of placing two speakers and a microphone in an earplug, using the speakers to excite the mechanical response of the eardrum, and using the microphone to sense the response of the ear to the sound stimulus. This response signal provides an indication of the health of the auditory system. This method of hearing assessment is supra-threshold; it allows the test to be performed quickly, by relatively unskilled personnel; and since the procedure does not rely on the test subject to consciously respond, it takes the uncertainty of the human response out of hearing assessment. This hearing assessment method is particularly useful for hearing screening in infants, but is also routinely used in adult hearing conservation programs. Current DPAOE screening is best performed in carefully controlled, acoustically shielded environments which are not typically found in newborn nurseries or intensive care units; in pediatricians’ offices; in other clinical settings; or on the Space Station and Space Shuttle.

Creare’s feedforward, adaptive, active noise reduction system for DPOAE measurements combines innovative acoustic signal processing, active noise-control algorithms, and special-purpose hardware and software for data collection. The system consists of the following components:

• Ear probe. The ear probe consists of two speakers and one microphone, which are sealed in the ear canal with a rubber tip. An external microphone is also mounted on the back end of the probe facing the external environment.
• Amplifier, filter, interface and data conversion unit. A custom-made interface unit includes a low-noise amplifier/filter for microphone signal conditioning, interfaces to the probes, and a calibration microphone interface. The filtered and amplified signals are converted to digital format using analog-to-digital (A/D) converters.
• Computer system. All data handling and the user interface resides on a standard tablet computer. The data collection software calculates the power spectral density (PSD) of the recorded signal, the distortion product, and the noise floor.

Creare is currently developing a clinical prototype of the system which will be used in human subject tests on Earth and on the Space Station to show improved SNR of DPOAE measurements in both low and high noise background environments.