Dodecahedron Speaker Verification
Generation of sound fields for both sound transmission and reverberation time is an essential element of building acoustics. It is important that these fields are truly random in nature to ensure the validity and repeatability of the results. The controlling standards are BS EN ISO-16283-1 for transmission testing and BS EN ISO-3383-1 for reverberation time measurements. To meet these requirements several manufacturers are now offering dodecahedron speaker systems for use in these applications.
For sound transmission loss measurements, annex A of BS EN ISO-16283 requires each speaker system used to comply with a directivity specification. For reverberation measurements, including those made in support of transmission loss measurements, BS EN ISO 3388-1 has tighter tolerances on the omni-directionality of the speaker system for precision measurements. Both standards also require bi-annual verification of the speaker systems to confirm compliance with these standards. In both cases this bi-annual verification comprises a full 360° polar measurement and the calculation of a 30°gluiding arc response that is then compared with the 360°average polar response.
Campbell Associates calibration laboratory have developed a verification procedure to comply with these requirements; it mounts the dodecahedron speaker on a rotating spigot in an anechoic chamber which is then rotated through 360° passed a measurement microphone. Measurements are made for each 1°rotation and the gliding arc calculated and compared with the specifications. The example shows the effect of faulty speakers, i.e. no output, damaged speaker, such as scraping coils or damaged cone, and finally the return to normal operation after repair.
Dodecahedron Speaker Calibration
in CA Laboratory