The Deelen infrasound array for recording sonic booms and events of CTBT interest

The Seismology Division of the Royal Netherlands Meteorological Institute (KNMI) has build up expertise in infrasound measurements by investigating low frequency events in order to distinguish between seismic and sonic events. KNMI operates, amongst others, a sixteen element microbarometer array with an aperture of 1.5 km, the Deelen Infrasound Array (DIA). Sonic booms and events of Comprehensive Test Ban Treaty (CTBT) interest are recorded within the frequency range of 100 seconds and 40 Hertz. Recently, KNMI and Microflown Technologies B.V. started a collaboration concerning infrasound measurements. This paper reports the use of a novel sensor. The so-called Microflown [1] is an acoustic sensor, sensitive for frequencies from 0Hz up to 1kHz. The Microflown is developed at the University of Twente and commercialised by Microflown Technologies B.V [3]

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

A novel technique for measuring the reflection coefficient of sound absorbing materials

A new method to measure the acoustic behaviour of sound absorbing material in an impedance tube is presented. The method makes use of a novel particle velocity sensor, the microflown, and a microphone. The so-called p·u method is compared to three other methods of which the two microphone technique is well known. It is shown that the combination of a microphone and a microflown provides direct information on the acoustic impedance, the sound intensity and the sound energy density. The experimental results are compared to the results obtained with the conventional impedance tube measurements. To be able to repeat the measurements in a reliable way a well described test sample with a quarter-wave resonator is used. Furthermore it is shown that the viscothermal effects on the wave propagation are important, i.e. for the quarter-wave resonator and to a lesser extent for the impedance tube itself

Statistical learning in children with a family risk of dyslexia

The assumption that statistical learning is affected in dyslexia has generally been evaluated in children and adults with diagnosed dyslexia, not in pre‐literate children with a family risk (FR) of dyslexia. In this study, four‐to‐five‐year‐old FR children (n = 25) and No‐FR children (n = 33) completed tasks of emerging literacy (phoneme awareness and RAN). They also performed an online non‐adjacent dependency learning (NADL) task, based on the Serial Reaction Time (SRT) task paradigm. Children's accuracy (hits), signal sensitivity (d′) and reaction times were measured. The FR group performed marginally more poorly on phoneme awareness and significantly more poorly on RAN than the No‐FR group. Regarding NADL outcomes, the results were less straightforward: the data suggested successful statistical learning for both groups, as indicated by the hit and reaction time curves found. However, the FR group was less accurate and slower on the task than the No‐FR group. Furthermore, unlike the No‐FR group, performance in the FR group varied as a function of the specific stimulus presented. Taken together, these findings fail to show a robust difference in statistical learning between children with and without an FR of dyslexia at preschool age, in line with earlier work on older children and adults with dyslexia

A numerical study of a method for measuring the effective in situ sound absorption coefficient

The accuracy of a method [Wijnant et al., “Development and applica- tion of a new method for the in-situ measurement of sound absorption”, ISMA 31, Leuven, Belgium (2010).], for measurement of the effective area-averaged in situ sound absorption coefficient is investigated. Based on a local plane wave assump- tion, this method can be applied to sound fields for which a model is not available. Investigations were carried out by means of finite element simulations for a typical case. The results show that the method is a promising method for determining the effective area-averaged in situ sound absorption coefficient in complex sound fields

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