An intuitive handheld acoustic noise source finder

ABSTRACT - An apparatus has been developed to find acoustic sound sources in the near field of a radiating object operating in a noisy environment. It is based on two orthogonally placed particle velocity probes (two Microflowns[1], [2]). The complete signal processing is done in real time with battery powered analogue circuitry, resulting in a very small and handheld measurement device. One Microflown is used to display the sound level and to listen to the source whilst rejecting the background noise and another Microflown is used to create a stereo\ud indication in which direction the device must be moved to pinpoint the noise source

Modeling and characterization of the sensitivity of a hot-wire particle velocity sensor

The sensitivity of an innovative acoustic sensor composed of four hot-wires is analyzed. An analytical model is presented that describes both the air flow and the temperature distribution in and around the probe. The presence of the chip surface in the vicinity of the wires influences the acoustic flow, while it also affects the temperature distribution. Both effects result into a specific angular dependence of the sensor sensitivity.\ud Acoustic measurements are compared with theory, showing good correspondence

Fully integrated three dimensional sound intensity sensor

For the first time, a complete 3-dimensional sound intensity sensor – consisting of 4 particle velocity sensors and a pressure microphone – has been integrated on a single chip, providing the possibility to do nearly point measurements of acoustic particle velocity, sound pressure, and therefore sound intensity. Principally the sensor consists of two distinct designs; a pressure sensor and particle velocity sensors. In this paper the design of the sensor, fabrication and measurement results are discussed and compared with theoretical results

On the Use of Various Oscillatory Air Flow Fields for Characterization of Biomimetic Hair Flow Sensors

To determine the characteristics of flow sensors, a suitable source for flow generation is required. We discuss three different sources for oscillating air flow, by considering their acoustic impedance, frequency range, velocity and ability to distinguish between flow and pressure. We discuss the impact of these sources on characterization of our biomimetic hair flow sensors, which operate at flow velocities from 1–100 mm/s within a frequency range from 10–1000 Hz

Analysis of packaging effects on the performance of the microflown

The packaging effects of an acoustic particle velocity sensor have been analysed both analytically and by means of finite volume simulations on fluid dynamics. The results are compared with acoustic experiments that show a large magnification of the output signal of the sensor due to the mounting inside a cylindrically shaped package. The influences of the package consist of a decrease of the output signal at frequencies below 1 Hz, whereas signals with frequencies above 10 Hz are amplified by a constant factor of approximately 3.5 (11 dB). The analysis leads to an improved insight into the effects of viscosity and fluid flow that play a role in flow sensing and opens the way for further optimisation of sensitivity and bandwidth of the sensor

A Three Dimensional Microflown

An integrated three dimensional acoustic particle velocity sensor is realized. The integration of multiple sensors on a single silicon die leads to improvements in terms of better a better reproducible sensor and a very small sensor to sensor distance allowing accurate single point measurements. Initial measurements performed show that three dimensional noise source finding is possible with this sensor

Listening to MEMS: An acoustic vibrometer

new way to characterize vibrating MEMS devices is presented. Using an acoustic particle velocity sensor the coupled sound field is measured, which is a measure for the movement of the MEMS device. We present several possible applications of this measurement method. It can be used as a read-out system for a mass flow sensor, and for characterization of in- and out-of-plane movements of MEMS devices. The method is an interesting alternative to laser scanning vibrometry due to its small size and low complexity; furthermore, it allows the user to `listen' directly to MEMS devices

Directional sensitivity of a three dimensional particle velocity sensor

The omni-directional sensitivity pattern of an integrated three dimensional acoustic sensor, composed of four hot-wire particle velocity sensors is analyzed theoretically and experimentally. We investigate the influence of the presence of the probe surface on the direction of the measured particle velocity measured by the sensors, and a description of the gas flow profile around the integrated sensor is presented.\u

Hydrophone pump, container and method therefor

The present invention relates to a hydrophone pump, and container and method therefor. The hydrophone pump comprises: - a housing provided with a reactor chamber; - an inlet for admitting and discharging fluid into and out of the reactor chamber; and - a piezo-element provided drivably on at least one side of the reactor chamber

Choosing the most appropriate sensor for acoustic measurements

In this paper examples of acoustical measurements are given where the use of an array consisting only of p-sensors does not give good results. An improvement is obtained when besides the p-sensor array, particle velocity sensors (v-sensors) are used as reference signals. in the "acoustic camera" experiments more information, i.e. a better picture is obtained when using p-sensors as well as v-sensors