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This paper describes a method that allows accuracy and bandwidth enhancements in 3-D sound intensity measurements. Commercial 3-D probes are usually set up with three mutually perpendicular 1-D p-p probes and, thus, arranged with six microphones; although sound intensity can be calculated with 15 independent pairs of transducers, only the three "primary" pairs that are aligned with the coordinate system axes. The other 12 "secondary" pairs consist of mutually perpendicular microphones, which are placed at a distance that is √2 times shorter than the primary one. The main idea of the proposed method is to average the intensity that is measured on primary and secondary pairs. This leads to a larger bandwidth, thanks to the shorter separating distance between secondary pairs. The intrinsic p-p method high- frequency sensitivity loss is partially recovered, starting from the theoretical plane wave expression. Measurements of different axes are weighted with coefficients that are computed by optimizing the measurement uncertainty. Errors that are due to the metrological characteristics of the transducers and the effects of environmental conditions are compensated. Experimental results showed that a p-p probe arranged with half-inch microphones that are placed at a distance of 50 mm allows reliable measurements up to 2.5 kHz, whereas a commercial probe bandwidth with the same configuration is usually 1250 Hz. [ABSTRACT FROM AUTHOR]

Very often in environmental and industrial acoustics, it is necessary to identify the contribution of single sources to global sound levels. Under this perspective, interests arise from the necessity of controlling noise or verifying whether a single source exceeds legal limits while there are other active sources around. Currently available methods are typically based on coherence or expert system techniques. Both approaches have relevant limitations, but for current purposes, coherence methods are usually more robust, particularly if carried out using vibration sensors in vibroacoustic interactions. Nevertheless, when a measurement system has to be based only on microphone measurements, those methods also have too little reliability and unsatisfying accuracy. In fact, it is quite impossible to eliminate in the input signals the effects of other sources, which usually also have some coherence with the output signal. In this paper, a relevant enhancement to coherence-based methods is described and discussed. The proposed approach leverages on the use of an acoustic intensity measurement approach instead of the sound pressure one. Method advantages and limitations are addressed with a theoretical approach; method performances are experimentally verified. [ABSTRACT FROM AUTHOR]