Integrated 3D Sound Intensity Probe (TET.6407)

Research:
Sound is characterized by two quantities, namely pressure and the so-called particle velocity. Our ears and microphones are only sensitive for pressure. Sound intensity comprises of a product of these quantities. It is measured using a certain combination of microphones, which is quite expensive and complex. In this project we shall combine a new type of sensor with a microphone in a way that the sound intensity (its direction and amplitude) can be measured by a small, simple system. This new type of sensor is called a microflown, which is nothing else than a fast flow sensor. It picks up the minute flow of air in sound waves - the particle velocity. Three mutually perpendicular microflowns combined with a microphone serve as a sensor for sound in intensity. Microflowns and microphone both can be fabricated using silicon micromachining (a manufacturing techniques derived from integrated circuit technology). Prototypes of this sensor - consisting of manually assembled components - show promising performance, however they still are bulky. Their size, design and inaccurate assembly seriously limit their performance in terms of noise, sensitivity, reproducibility and frequency response. The new aspect in this project is that microflowns and one microphone will be integrated into a single chip in one fabrication process without need for further assembly of miniature parts. In this way one obtains a point like (1 - 2 mm3) probe with greatly increased performance and possibly reduced production cost. The scientific challenges result from the complexity of the system and are in fabrication issues, design and the physics (heat transfer in a dynamic medium, noise). In particular research will concentrate on: finding fabrication processes for microflowns pointing in three perpendicular directions, combine it with the fabrication process for a silicon microphone, study characteristics of the sensor and its parts, optimize the system to make it more sensitive to high frequencies, understand and reduce noise, and finally to understand and exploit influences of the packaging of the sensor on its performance.

Utilization:
In this project we want to do research on a sensor for sound intensity such that not only the noise level but also the direction to the noise source can be measured. The sensor can locate sources of the sound. The measurement of sound intensity is the key for the control of noise caused by e.g. traffic (cars, railway, airplanes) and industry. For this purpose only expensive measurement equipment exists which has to be used by specialized personnel. A sensor would be quite helpful in this field. Further such a sensor is needed for detailed studies of the emission of sound (for scientific and engineering purposes), and to study and implement systems for noise cancellation. Due to the fabrication technology used for the realization of the sensor it will be possible to sell the sensor for much lower prices than systems currently available. This might open a complete new market.
This project will be carried out in close collaboration with and support by Microflown Technologies, a start up company which intends to commercialize the Microflown.

More information can be found on the website of the reserach group and on the website of Microflown Technologies.

Apart from Microflown Technologies, 5 other companies are involved in this project.