The typical human cochlea operates over a two and a half decade frequency band, from 20 Hz-20 kHz, covers 120 dB of dynamic range, and can distinguish tones which differ by less than 0.5%. Sounds as quiet as 0 dB SPL (20 .mu.Pa RMS) can be heard. Humans are also able to discriminate sounds temporally with spacing as small as 10-20 .mu.s. Marine mammals such as whales hear over an even broader band than humans, utilizing acoustic signals for communication (at low frequencies) and navigation (high frequency “SONAR”). One difference between submerged and in-air operation is that the middle ear impedance matching functions may be inactive or modified in marine mammals due to the different characteristic impedance of the environment.
University of Michigan researchers have invented a micro machined fluid-structure system capable of acoustic sensing and mechanical frequency analysis. The system acts as a passive mechanical filter. A capacitive sensing scheme is incorporated into the micro machined structure to produce multiple channels of filtered output, each sensitive to a particular frequency band. The major technical innovation, which differentiates this device from others, is the inclusion of both “cochlear-like” fluid structure mechanics and integrating sensing elements into a single micro-machined device, producing a sensor/filter which functions like the human ear.
Applications and Advantages
- Acoustic sensors for commercial, scientific-nl-and medical applications
- Acoustic sensors for military applications-nl-such as unattended sensors, handheld sonar,-nl-or autonomous vehicles
- Low cost
- High sensitivity
- Small size