John Bassett

While there exists research on electroacoustic and spatial music specifically composed for an environment, very little is written on the more improvisational aspect of performing an acoustic instrument in a particular space, and letting the space inform the musical direction and content. A solo piano recording project was undertaken at the Auckland Town Hall Concert Chamber with this concept as its focus. This paper documents the musical and cognitive processes involved in responding to the particular environment, and provides technical analyses of both the recording and room acoustics to determine possible correlations.

The acoustic environment of an auditorium stage can enhance the ability of musicians or actors to hear each other clearly. This is assessed through a set of parameters called 'stage support'. Stage support parameters are conventionally measured using an omnidirectional source and microphone separated by 1 m on the stage. Various stage support parameters are derived from energy ratios of the direct and reflected (or reverberant) sound in the impulse response from source to microphone. The present paper examines the possibility of assessing the directional characteristics of the reflected soundfield by using a multidirectional microphone. Measurements were made in the Sydney Theatre Company's 'Sydney Theatre' with and without a stage set. The microphone used allows first order spherical harmonic decomposition of the soundfield, which was transformed to cardioid components for orthogonal directions (upstage, downstage, left, right, up and down), as well as for horizontal rotations of the cardioid microphone. These were used to calculate directional stage support values. Results demonstrate the potential of this simple extension of standard stage support measurement by showing the acoustical effect of the set.

An ambisonic microphone was used to measure the degree to which a sound field varied with direction within a reverberant room. The apparent diffusivity of the room was varied by incrementally adding reflecting panels, according to AS ISO354 2008, producing seven different room states. In each reverberation time was measured using three loudspeaker positions and four measurement microphone positions, according to the interrupted noise method outlined in AS ISO354 2008. Recordings were made of sinusoidal sweeps for the three loudspeaker positions with a first order ambisonic microphone at three different positions in the room. The recorded sine sweeps were converted to impulse responses to measure the evenness of the sound field around the microphone in each room state. These results are compared with the traditional method of establishing a diffuse state in a reverberation room with a view to the development of a more direct method for establishing an isotropic state in reverberant rooms.

Opera performance conveys both visual and auditory information to an audience, and so opera theaters should be evaluated in both domains. This study investigates the effect of static visual and auditory cues on seat preference in an opera theater. Acoustical parameters were measured and visibility was analyzed for nine seats. Subjective assessments for visual-only, auditory-only, and auditory-visual preferences for these seat positions were made through paired-comparison tests. In the cases of visual-only and auditory-only subjective evaluations, preference judgment tests on a rating scale were also employed. Visual stimuli were based on still photographs, and auditory stimuli were based on binaural impulse responses convolved with a solo tenor recording. For the visual-only experiment, preference is predicted well by measurements taken related to the angle of seats from the theater midline at the center of the stage, the size of the photographed stage view, the visual obstruction, and the distance from the stage. Sound pressure level was the dominant predictor of auditory preference in the auditory-only experiment. In the cross-modal experiments, both auditory and visual preferences were shown to contribute to overall impression, but auditory cues were more influential than the static visual cues. The results show that both a positive visual-only or a positive auditory-only evaluations positively contribute to the assessments of seat quality.

The Sydney Opera House Trust is considering making changes to its Concert Hall. Prior to any alteration, the Acoustics group at the University of Sydney has sought to document the hall. The main measurements were made for 48 receiver locations and 6 source locations, using omnidirectional measurement microphones, B-format (Soundfield) microphones and dummy head microphones in every receiver position. The measurements included impulse responses, anechoic music recordings, and recordings of a calibrated sound power source. Results documented by previous practitioners and researchers are described and comparison is made with the recent results.