Measurement of room acoustic parameters with an omnidirectional parametric loudspeaker in an converted chapel for choral music performance

Abstract

An omnidirectional parametric loudspeaker (OPL) is a sound source made of hundreds of ultrasonic transduc ers arranged in a spherical configuration. Each transducer emits ultrasonic waves and, due to the nonlinear effects of air, these waves generate audible sound within the ul trasonic beam. Compared to a dodecahedron loudspeaker, the OPL offers improved omnidirectionality, although it operates at lower sound pressure levels (SPLs). Exponen tial sine sweeps have shown to be very effective with this new type of loudspeaker, which opens the door to using it in some acoustic tests. This paper explores the perfor mance of the OPL in measuring room acoustic parame ters, such as reverberation time, early decay time, defini tion and clarity. The case study selected is the Pere Pruna Civic Center in Barcelona. Originally built as a single nave chapel in the early 20th century, the building was re stored and converted for civic use in the late 20th century. It is currently used mainly for choral music, with a ca pacity for about 80 people. Acoustic measurements were conducted according to ISO 3382-1 using the OPL and a commercial dodecahedron loudspeaker. The results show that the OPL performs well in mid and high frequencies, although it requires higher SPLs at low frequencies.