Abstract
The scattering phenomenon is known to be of great importance for the acoustic quality of a performance arts space. The scattering of sound can be achieved in different ways: it can be obtained by the presence of architectural and/or decorating elements inside a room (e.g., columns, statues), by the geometry and roughness of a surface (e.g., Quadratic Residue Diffuser (QRD)) and by the diffraction effect occurring when a sound wave hits the edges of an obstacle. This article deals with the surface scattering effects and the diffusion phenomenon only related to MDF and plywood panels tested by disposing the wells both horizontally and vertically. The test results undertaken inside a semi-reverberant room and inside a large reverberant room have been compared to highlight the success and the failure of the measuring methodologies. In detail, according to the existing standards and regulations (i.e., ISO 17497—Part 2), diffusion measurements have been undertaken on a few selected types of panel: two QRD panels (made of Medium Density Fiberboard (MDF) and plywood) with and without a smooth painted solid wood placed behind the QRD. The panels have been tested inside two rooms of different characteristics: a semi-anechoic chamber (Room A) and a large reverberant room (Room B). The volume size influenced the results that have been analyzed for both chambers, showing an overlap of reflections on panels tested inside Room A and a clear diffusion response for the panels tested inside Room B. In terms of the diffusion coefficient in all the octave bands between 125 Hz and 8 kHz, results should not be considered valid for panels tested in Room A because they were negatively impacted by extraneous reflections, while they are reliable for panels tested in Room B.
Highlights
Introduction iationsThe acoustic properties of surfaces are essential to estimate and calculate sound propagation within an enclosed space [1,2]
Diffusing panels made of two different materials
This is not due to the ability of the panel to the central microphones and the lateral ones. This is not due to the ability of the panel to reflect a lot of lateral energy, but it might be caused by the small dimensions of rooms of different characteristics: a semi-anechoic chamber (Room A) that reflect a lot of lateral energy, but it might be caused by the small dimensions of Room A
Summary
The acoustic properties of surfaces are essential to estimate and calculate sound propagation within an enclosed space [1,2]. The acoustic scattering from surfaces and sound absorption characteristics are very important in all aspects of room acoustics, e.g., in opera houses, concert halls, industrial workplaces and reverberation chambers. The sound scattering mechanism is activated by the corrugations of the walls with a sufficiently rough structure or by single elements such as columns, statues, etc., or by diffraction effects along the edges of panels. Concert halls or theatres could present focalization of the sound, so diffusing panels are inserted to solve this problem [3,4]. Many measurement methods have been developed to quantify the various types of sound scattering coefficients and to determine the sound diffusion mechanisms. Acoustical surface scattering has been deeply studied by researchers worldwide [5,6,7], and Licensee MDPI, Basel, Switzerland
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