/npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr Access and use of this website and the material on it are subject to the Terms and Conditions set forth at http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://dx.doi.org/10.1121/1.1787525Journal of the Acoustical Society of America, 116, 4, pp. 2138America, 116, 4, pp. -2148America, 116, 4, pp. , 2004 Measurements of directional properties of reverberant sound fields in rooms using a spherical microphone array Gover, B. N.; Ryan, J. G.; Stinson, M. R. AbstractThe directional variation of sound at a point has been studied in three rooms, using a measurement system described previously [J. Acoust. Soc. Am. 112, 1980Am. 112, -1991Am. 112, (2002]. The system uses a pair of 32-element spherical microphone arrays to obtain directional impulse responses in each of 60 steering directions, with an angular resolution of 28 degrees, covering all directions in the whole solid angle. Together, the array measurements span the frequency range from 300-3300 Hz. The angular distribution of incident sound energy is visualized on a three-dimensional plot, and quantified by computing the directional diffusion and the directional peak-to-average level difference ("anisotropy index") of the sound field. The small-to-medium sized rooms had reverberation times of 360, 400, and 600 ms. Measurements were made for several source and receiver locations in each, and were analyzed over several time ranges (full decay time of room, late time decay, 2 ms windows throughout the decay). All measured sound fields were found to be highly directional; the distribution of arriving energy at a point greatly influenced by the early specular reflections. The directions and arrival times of these reflections were identified from the measurements, giving excellent agreement with those expected from knowledge of the room geometry. It was observed that as time progressed, the sound fields initially exhibited increasing isotropy, followed by increasing anisotropy, due to nonuniform absorption in the rooms.The measurement system is capable of yielding detailed information about the reverberant sound field in a room, and is easily modified to be able to analyze ambient or time-varying fields.PACS numbers: 43.55. Mc, 43.55.Gx, 43.55.Br, 43.38.Hz Typeset using REVT E X Gover, JASA 3

A measurement system has been developed that is capable of analyzing the directional and spatial variations in a reverberant sound field. A spherical, 32-element array of microphones is used to generate a narrow beam that is steered in 60 directions. Using an omnidirectional loudspeaker as excitation, the sound pressure arriving from each steering direction is measured as a function of time, in the form of pressure impulse responses. By subsequent analysis of these responses, the variation of arriving energy with direction is studied. The directional diffusion and directivity index of the arriving sound can be computed, as can the energy decay rate in each direction. An analysis of the 32 microphone responses themselves allows computation of the point-to-point variation of reverberation time and of sound pressure level, as well as the spatial cross-correlation coefficient, over the extent of the array. The system has been validated in simple sound fields in an anechoic chamber and in a reverberation chamber. The system characterizes these sound fields as expected, both quantitatively from the measures and qualitatively from plots of the arriving energy versus direction. It is anticipated that the system will be of value in evaluating the directional distribution of arriving energy and the degree and diffuseness of sound fields in rooms.

No abstract

No abstract