An overview of microflown technologies

The Microflown is an acoustic sensor measuring particle velocity instead of sound pressure, which is usually measured by conventional microphones. Since its recent invention it is mostly used for measurement purposes (1D and 3D-sound intensity measurement and acoustic impedance). The Microflown is also used for measuring DC-flows, that can be considered as particle velocity with a frequency of 0Hz. Furthermore the Microflown is used in the professional audio as a low frequency add on microphone for pressure gradient microphones (figure of eight; directional microphones). Due to its small dimensions and silicon based production method the Microflown is very suitable for mobile applications like mobile telephones or smartcards. Nowadays sound-energy determination, array applications and three-dimensional impulse response are under investigation. Although the Microflown was invented only some years ago, the device is already commercially available

The microflown : a true particle velocity microphone; sound intensity application

The Microflown is world's first particle velocity microphone that enables numerous new acoustical applications, due to the combination of its unique acoustical performance and small dimensions. Several patents have been granted since its invention in 1994. This abstract will focus on one application: sound intensity measurements. The direct measurement of particle velocity makes it possible to measure sound intensity in one place. The advantage of this is that the complete audio band can be measured at once now, in the near field, far field and also both in reactive and nonreactive fields. With the use of the Microflown, the realisation of very small three dimensional sound intensity probes will become feasible soon. Some background information of the microflown concerning the manufacturing, signal and noise properties and preamplifiers will be presented

The microflown, from die to product

This article reports on various steps to transform a concept to a product. A sound intensity probe based on a micro-machined acoustic sensor "the Microflown" is used as an example. Requirements for the micromachined part are simplicity and uncomplicated processing to reach a high throughput. For monitoring the quality, simple and reliable characterisation tools should be designed as well. To gain credibility independent labs should test the product. The product should offer a complete solution that competes in overall costs and performance, and it must be possible to connect it into existing systems

Source localization using acoustic vector sensors: a music approach

Traditionally, a large array of microphones is used to localize multiple far field sources in acoustics. We present a sound source localization technique that requires far less channels and measurement locations (affecting data channels, setup times and cabling issues). This is achieved by using an acoustic vector sensor (AVS) in air that consists of four collocated sensors: three orthogonally placed acoustic particle velocity sensors and an omnidirectional sound pressure transducer. Experimental evidence is presented demonstrating that a single 4 channel AVS based approach accurately localizes two uncorrelated sources. The method is extended to multiple AVS, increasing the number of sources that can be identified. Theory and measurement results are presented. Attention is paid to the theoretical possibilities and limitations of this approach, as well as the signal processing techniques based on the MUSIC method

Three-dimensional sound intensity measurements using microflown particle velocity sensors

This paper reports on a novel method to measure three-dimensional sound intensity and the fabrication of a miniature three-dimensional sound intensity probe. Verifying measurements where performed with three separate micromachined particle velocity probes and one pressure microphone. A three-dimensional sound intensity probe has been realised based on a three-dimensional micromachined particle velocity microphone, a 3D Microflown, and a miniature pressure microphon