Design and implementation of a multi-octave-band audio camera for realtime diagnosis

Noise pollution investigation takes advantage of two common methods of diagnosis: measurement using a Sound Level Meter and acoustical imaging. The former enables a detailed analysis of the surrounding noise spectrum whereas the latter is rather used for source localization. Both approaches complete each other, and merging them into a unique system, working in realtime, would offer new possibilities of dynamic diagnosis. This paper describes the design of a complete system for this purpose: imaging in realtime the acoustic field at different octave bands, with a convenient device. The acoustic field is sampled in time and space using an array of MEMS microphones. This recent technology enables a compact and fully digital design of the system. However, performing realtime imaging with resource-intensive algorithm on a large amount of measured data confronts with a technical challenge. This is overcome by executing the whole process on a Graphic Processing Unit, which has recently become an attractive device for parallel computing

Biomimetic direction of arrival estimation for resolving front-back confusions in hearing aids

Sound sources at the same angle in front or behind a two-microphone array (e.g., bilateral hearing aids) produce the same time delay and two estimates for the direction of arrival: A front-back confusion. The auditory system can resolve this issue using head movements. To resolve front-back confusion for hearing-aid algorithms, head movement was measured using an inertial sensor. Successive time-delay estimates between the microphones are shifted clockwise and counterclockwise by the head movement between estimates and aggregated in two histograms. The histogram with the largest peak after multiple estimates predicted the correct hemifield for the source, eliminating the front-back confusions

Directional speech acquisition using a MEMS cubic acoustical sensor microarray cluster.

This thesis presents the design of a directional speech acquisition system using a MEMS cubic acoustical sensor microarray cluster to improve speech intelligibility in a noisy reverberant acoustical environment. In the proposed system, five identical acoustical sensor arrays constitute the five sides of a cubic geometry whereas the other side of the cube is to be used for interconnection and packaging purposes. Each of the sensor microarrays is associated with two beam shapes: a main beam to acquire speech signal from a particular direction and a scanning beam to locate and track a potential speech source. A microelectronics based beam synthesis engine controls the selection of a main beam to acquire speech signals from a particular direction based on the output level of the five scanning beams. In this way the developed system provides an improved reduced noise dynamic directional speech acquisition system covering a 3-D space. (Abstract shortened by UMI.)Dept. of Electrical and Computer Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2006 .H8. Source: Masters Abstracts International, Volume: 45-01, page: 0411. Thesis (M.A.Sc.)--University of Windsor (Canada), 2006

Thin-Film PZT based Multi-Channel Acoustic MEMS Transducer for Cochlear Implant Applications

AuthorThis paper presents a multi-channel acoustic transducer that works within the audible frequency range (250-5500 Hz) and mimics the operation of the cochlea by filtering incoming sound. The transducer is composed of eight thin film piezoelectric cantilever beams with different resonance frequencies. The transducer is well suited to be implanted in middle ear cavity with an active volume of 5 mm × 5 mm × 0.62 mm and mass of 4.8 mg. Resonance frequencies and piezoelectric outputs of the beams are modeled with Finite Element Method (FEM). Vibration experiments showed that the transducer is capable of generating up to 139.36 mVpp under 0.1 g excitation. Test results are consistent with the FEM model on frequency (97%) and output voltage (89%) values. Device was further tested with acoustic excitation on an artificial tympanic membrane and flexible substrate. Under acoustic excitation, 50.7 mVpp output voltage generated under 100 dB Sound Pressure Level (SPL). Output voltages observed in acoustical and mechanical characterizations are the highest values reported to the best of our knowledge. Finally, to assess the feasibility of the transducer in daily sound levels, it was excited with a speech sample and output signal was recovered. Time-domain waveforms of the recorded and recovered signals showed close patterns

Lateral-Line Inspired MEMS-Array Pressure Sensing for Passive Underwater Navigation

This paper presents work toward the development of a novel MEMS sensing technology for AUVs. The proposed lateral line-inspired sensor system is a high-density array of pressure sensors for measuring hydrodynamic disturbances. By measuring pressure variations on a vehicle surface, a dense pressure sensor array will allow the AUV to detect, classify, and locate nearby obstacles and optimize its motion in unsteady environments. This approach is very similar to the canal lateral line system found in all fish, which allow them to function in dark or clouded environments. In order to lay the groundwork for developing the MEMS sensor and interpreting the pressure distributions, the paper also presents experiments demonstrating the discrimination between cylindrical obstacles of round and square cross sections with an array of off-the-shelf pressure sensors. Test objects with 5.1 cm and 7.6 cm diameters passed stationary sensors at 0.5 m/s and 0.75 m/s and with 1.3 and 5.1 mm separation. Hand chosen features and features chosen through a Principal Component Analysis are used to discriminate between object shapes under a variety of conditions. A classification error rate of under 2% is achieved across all velocities, sizes, and separations. These results lead to requirements for the density, sensitivity, and frequency response of the MEMS sensors, which fall well in the MEMS domain. The pressure sensor array proposed here consists of hundreds of MEMS pressure sensors with diameters near 1 mm spaced a few millimeters apart fabricated on etched silicon and Pyrex wafers; a fabrication process for producing the array is described. A strain-gauge pressure sensor is analyzed and shown to satisfy specifications as required by the results from the afore-mentioned experiments. The sensing element is a strain gauge mounted on a flexible diaphragm, which is a thin (20 µm) layer of silicon attached at the edges to a square silicon cavity 2000 µm wide on a side. A source voltage of 10 V produces a sensor with a sensitivity on the order of 1µV/Pa. Since the thermal noise voltage is near 0.7 µV, the pressure resolution of the sensors is on the order of 1 Pa.United States. National Oceanic and Atmospheric Administration (Grant NA06OAR4170019 Project R/RT-2/RMC-17