Andrei N. Chesnokov
Lab. of Architectural Acoust., Res. Inst. of Bldg. Phys., Locomotivny pr. 21, Moscow 127238, Russia
An investigation of acoustics in 15 circuses with fabric roofs has been carried out. Objective acoustical parameters (reverberation time, clarity C[sub 80], and others) have been measured and questionnaires from the audience in the circuses have been obtained. Features of circuses acoustics are the decrease in reverberation times at low frequencies, echo (in halls with impervious fabric roofs), and high levels of background noise. The background noise levels in circuses before a performance were equal L[sub A]=46--56 dBA. The questionnaire contained subjective acoustical attributes: Timbre, balance, reverberance, spaciousness, echo, loudness, clearness, audibility of background noise, background noise affect on speech legibility, and others. Average mark estimates and results of measured noise level in halls (L[sub A]) have been subjected to factor analysis. Three factors have been extracted that can be interpreted as (1) overall acoustical impression of the music sound in a circus, (2) disturbing influence of the background noise, and (3) clarity of music and speech sounding.