Near-field acoustical holography has been shown to be a useful tool for visualizing jet noise fields. It has been applied to a full-scale jet on an installed military aircraft with promising results, but the source characteristics in the extreme near field have been difficult to characterize because of the interference of acoustic reflections off the rigid reflecting plane beneath the jet. To p...

Computer simulations can be used to generate the spatial and temporal data describing the acoustical behavior of performance halls, but typically the analytical results are difficult to assimilate and compare. By using c o m p u t e r graphics to display the multi-dimensional data, substantially greater amounts of information than that conveyed by standard techniques can he communicated to the ...

This short note describes some simple acoustical wave experiments that explain the physics of reflection and transmission coefficient formulae for normal incidence P-waves. The experiments help us to understand the mathematical expressions for the reflection and transmission coefficients for displacement and pressure that are frequently used in seismology. Figure 1. The figure shows a boundary ...

The perturbation analysis of an ideal acoustical duct was first made by Rayleigh in 1878 and the result has since stood in the literature. However, the analysis is based on the assumption of potential and kinetic energy densities that remain constant as a change in cross section occurs, whereas, in fact, they may fluctuate significantly in comparison to the slowly varying "wave function," Psi(x...

This paper reports the results of reproducibility experiments on the interlaboratory characterization of the acoustical properties of three types of consolidated porous media: granulated porous rubber, reticulated foam, and fiberglass. The measurements are conducted in several independent laboratories in Europe and North America. The studied acoustical characteristics are the surface complex ac...

After decades of development room acoustical computer models have matured. Hybrid methods combine the best features from image source models and ray tracing methods and have lead to significantly reduced calculation times. Due to the wave nature of sound it has been necessary to simulate scattering effects in the models. Today's room acoustical computer models have several advantages compared t...

The parameters of moving-coil loudspeaker drivers are typically determined using direct electrical excitation and measurement. However, as electro-mechano-acoustical devices, their parameters should also follow from suitable mechanical or acoustical evaluations. This paper presents the theory of an acoustical method of excitation and measurement using normal-incidence sound transmission through...

The personal quality of sustained vowels uttered by eight male talkers was represented multidimensionally in a psychological auditory space (PAS) by means of Kruskal’s multidimensional scaling procedure based on the perceptual confusion in talker discrimination tests. Physical properties of the vowels were analyzed in terms of elementary acoustical parameters, such as formant frequencies, slope...

After decades of development room acoustical computer models have matured. Hybrid methods combine the best features from image source models and ray tracing methods and have led to significantly reduced calculation times. Due to the wave nature of sound it has been necessary to simulate scattering effects in the models. Today's room acoustical computer models have several advantages compared to...

Non-contact ultrasonic, enables rapid testing of structures using ultrasonic tests that are not possible via conventional contact transducers. This paper reports on laser ultrasonic and air/gas coupled ultrasonic measurements that are performed remotely, do not require direct access to test area, do not need traditional ultrasonic coupling and do not have traditional C-scan fixture requirements...