Corrected Statistical Energy Analysis Model in a Non-Reverberant Acoustic Space

Statistical Energy Analysis(SEA)is a well-known method to analyze the flow of acoustic and vibration energy in a complex structure.This study investigates the application of the corrected SEA model in a non-reverberant acoustic space where the direct field component from the sound source dominates the total sound field rather than a diffuse field in a reverberant space which the classical SEA model assumption is based on.A corrected SEA model is proposed where the direct field component in the energy is removed and the power injected in the subsystem considers only the remaining power after the loss at first reflection.Measurement was conducted in a box divided into two rooms separated by a partition with an opening where the condition of reverberant and non-reverberant can conveniently be controlled.In the case of a non-reverberant space where acoustic material was installed inside the wall of the experimental box,the signals are corrected by eliminating the direct field component in the measured impulse response.Using the corrected SEA model,comparison of the coupling loss factor(CLF)and damping loss factor(DLF)with the theory shows good agreement.

Preliminary Archaeoacoustic Study of Kanheri Caves in Mumbai(Maharashtra,India)

Here we report first ever study on acoustical evaluation of Kanheri Caves located in Sanjay Gandhi National Park,Mumbai(Maharashtra,India).These caves are dated to a period between 2nd century BCE to 7th century CE.In this study we used an ambisonic recorder to capture Impulse Response,which carries acoustic signature of the place.Out of total 109 caves 41 were surveyed in available time.Out of those reverberant environment was noted in 12 caves.Measurements were made only in 3 caves(Cave Nos.1,3,11)which are important.In the beginning we carried out an FFT analysis.We then studied room acoustic parameters like Reverberation Time,Early Decay Time,Clarity,Definition,etc.,based on the measurement of Impulse response.Cave No.3 have high value of reverberation time,compared to other.Therefore it also have lower clarity compared to others.It is properties needs to be compared with similar structures(chaityas)in Maharashtra(at Ajanta,Ellora,Nashik,Junnar,etc.)and elsewhere in India.It is worthwhile to carry out further research in Cave No.3 with more sophisticated instruments as well as 3D modeling.Since the experiment was performed with receiver at only one position,we also suggest to carry out experiment with receiver at multiple positions and then comparing them.

Acoustic Characteristics Analysis of Industrial Premises with Process Equipment

Process equipment placing in industrial premises leads to essential change of room acoustic characteristics: mean length of sound rays’ free runs, reverberation time and mean absorption factor in a room. The changes influence distribution of the reflected sound energy in premise volume. Failure to take account of the given circumstance results in errors at definition of sound pressure levels and an estimation of efficiency of building-acoustic measures of noise abatement. In the paper the results of computer modeling of acoustic processes in premises with the process equipment are considered and influence of the equipment on a sound absorption indoors is analyzed. The computer simulation is carried out on the basis of the ray tracing method with taking into account rays’ energy distribution in a room. It is shown that such approach allows determining objectively the integral acoustic characteristics of industrial premises, takes into account influencing to them the room parameters, the presence and scattering characteristics of the equipment and makes more accurate the equations putting into engineering practice.