SBIR-STTR Award

This proposal, in its second revision, focuses on improving effective S/N ratios for hearing aids and cochlear implants by means of a technique that increases gain when a signal causes the total in-band energy to become greater. By means of the appropriate design of signal- conditioning circuit elements, together with the inclusion of a directional microphone in the system, it is possible to improve the directional selectivity of the receiver. The consequent effective increase in the signal/noise ratio should of course improve intelligibility of the speech stream. As part of another research project, this system is being incorporated into a device designed as a tactile aid for hearing-impaired persons.

Thesaurus Terms:
biological signal transduction, biomedical equipment development, hearing aid, noise, speech recognition clinical biomedical equipment, cochlear implant, electrotactile communicationFood and Drug Administration (FDA)

The Phase I study demonstrated that combining a directional microphone with a new noise processing method resulted in SIN improvements on the order of 10 dB as compared to an omni-directional microphone and no processing used in the same setting. Consequences for hearing impaired subjects with losses ranging from moderate to severe was to restore their performances to be statistically equivalent to that measured in quiet. Even more powerful was that for three out of four of the subjects evaluated using the best realization of the method, performances were numerically equivalent in both noise and quiet where the original SIN was 0 dB. The processing method is called Time Domain Noise Filtering (TDNF) and has been granted a US Patent. During this Phase II work we will implement the method in digital technology using a Digital Signal Processor (DSP) to make it compatible with digital hearing aid technology. At the same time, the greater flexibility of DSP technology, as compared to the analog methods used in the Phase I work, will be exploited to make the method adaptable to changing noise levels and to explore the dynamics of the method that might improve its performance even more. We will study a range of hearing impaired subjects including cochlear implant users. We have contacted both a hearing aid company and a cochlear implant company regarding use of the TDNF method in their devices. Letters from the companies are included in this application.