Volume 119, Issue 2, February 2006
Index of content:
- ACOUSTICAL MEASUREMENTS AND INSTRUMENTATION 
119(2006); http://dx.doi.org/10.1121/1.2151811View Description Hide Description
Sound intensity probes are often used with windscreens to minimize the effect of noise caused by airflow. A theoretical and experimental study of the effect of windscreens on intensity probes published ten years ago concluded that windscreens give rise to underestimation of the sound intensity at low frequencies in strongly reactive sound fields. The theoretical part of this study was based on the assumption of a windscreen of infinite extent. In this paper windscreens of realistic size and shape are dealt with by means of a coupled boundary element model for the windscreen and the surrounding air. The error of the estimated intensity caused by the windscreen is calculated under a number of sound field conditions of varying reactivity. It is shown that the resulting error can be much larger than the intensity itself in a very reactive sound field. It is also shown that the shape and size of the windscreen has a significant influence on the error.
119(2006); http://dx.doi.org/10.1121/1.2151797View Description Hide Description
In a sound field disturbance of pressure,particle velocity, density, temperature, and energy occur. In this paper acoustic disturbances in air are considered. In the majority of papers on acoustics only changes in the sound pressure are reported while in this paper results on the particle velocity are reported. Since particle velocity is a vector, while the pressure is a scalar, more information can be obtained when using a particle velocitysensor instead of a pressuresensor (microphone). Four particle velocitysensors are combined to one (small) device. In a reverberant room the four autospectra and the six cross spectra are determined. Interpretation of the measured results gives information of the free field (sound field without a contribution of reflections) as well as of the reverberant field.