Opera Singer Vocal Directivity

Opera Singer Vocal Directivity This project measured the vocal directivity of eight professional opera soloists. Measurements were made in an anechoic room, a reverberant room, and a recital hall. Results show that the vocal directivity of singers does vary between singers, but not between types of singing projection (using operatic singing styles). Comparison with previous studies show opera singling to be significantly more directional than choral singing or conversational speech. This project was funded by an Australian Research Council grant involving Prof. Pamela Davis, Dr Densil Cabrera and Anna Connolly. Students and ex-students involved included David Gilfillan, Sam Ferguson, Konrad Skirlis, and Alan Subkey. K. Skirlis, D. Cabrera and A. Connolly (2005) "Spectral and temporal changes in singer performance with variation in vocal effort,"australian Acoustical Society Conference, Busselton, Australia D. Cabrera and P. Davis (2004) "Vocal directivity measurements of eight opera singers," International Congress on Acoustics, Kyoto, Japan

Airqube Sound Attenuation using Quarter-wave Resonators Airqube is an acoustic technology that lets in fresh air but blocks out 85% of incoming noise. Its acoustic performance is about the same as a closed and well sealed single glazed window. Air flow is the same as for a ventilator of the same area with no sound attenuation. It is being considered for a range of applications where natural ventilation and noise reduction is required. For example, Airqube is being sought for computer casings, wind turbines, automobiles, consumer products such as hair dryers, entertainment units and in the building and construction industry. The first application of Airqube technology has been used to create Silenceair, the building ventilator that lets in fresh air but blocks out incoming noise. Airqube was developed by Dr Chris Field in his PhD thesis, and was patented in 2003. Silenceair won Dr Field the ABC Inventor of the Year in 2004.

Auditory Perception of Room Size This series of studies investigates the auditory cues that give us the impression of room size. Experiments have been conducted in real rooms (blindfolded subjects), using headphones (binaural reproduction) and using loudspeakers (stereo-dipole). Results from several experiments all indicate that clarity index (the ratio of early to late energy in a room impulse response) is the best simple objective predictor of subjective room size impression. Comparison between different playback systems and the real room environment shows systematic differences. These studies have involved Megan Kwak (M.Des.Sci. honours student), Claudiu Pop (PhD student), Dr Daeup Jeong (former PhD student and visiting scholar) and Dr Densil Cabrera, as well as academics and research students at Parma University, Italy. D. Cabrera, C. Pop and D. Jeong (2006) "Auditory room size perception: a comparison of real versus binaural sound-fields," 1st Australasian Acoustical Societies' Conference, Christchurch, New Zealand C. Pop and D. Cabrera (2005) "Auditory room size perception for real rooms," Australian Acoustical Society Conference, Busselton, Australia D. Cabrera, A. Azzali, A. Capra, A. Farina and P. Martignon (2005) "Perceived room size and source distance in five simulated concert auditoria," 12th International Congress on Sound and Vibration, Lisbon, Portugal D. Cabrera, D. Jeong, H. J. Kwak and J.-Y. Kim (2005) "Auditory room size perception for modeled and measured rooms," Internoise, Rio de Janeiro, Brazil (invited paper) P. Martignon, A. Azzali, D. Cabrera, A. Capra, and A. Farina (2005) "Reproduction of auditorium spatial impression with binaural and stereophonic sound systems," 118th Audio Engineering Society Convention, Barcelona, Spain

Anechoic Lining Design Using Graded Flow Resistivity Materials An anechoic room is a room that absorbs all sound, limited by a low cutoff frequency that is determined by the internal lining thickness and details of its design. Traditional anechoic lining design uses fibreglass wedges to absorb the sound. Using evolutionary algorithms, this project developed optimized solutions for anechoic linings made from flat layers of commonly available materials. Not only is this approach cheaper than the traditional design, but it can provide greater sound absorption for a given lining thickness. This theory has been applied to the design of a new anechoic room at the University of Western Sydney, and a new partially anechoic room in the University of Sydney s School of Electrical and Information Engineering. The Acoustics Research Laboratory in Wilkinson building is being restored using this technique, following a fire. Jingfeng Xu is a PhD graduate and honorary associate. J. Xu, J., Nannariello and F.R. Fricke (2004) Optimising flat-walled multi-layered anechoic linings using evolutionary algorithms, Applied Acoustics 65: 1009-26 J. Xu, J.M. Buchholtz and F.R. Fricke (2006) Application of multi-layered polyurethane foams for flat-walled anechoic linings, Applied Acoustics 67: 476-485 J. Xu, J.M. Buchholtz and F.R. Fricke (2006) Flat-walled multilayered anechoic linings: Optimization and application, J. Acoust. Soc. Am. 118: 3104-3109

Acoustic Quality of a Stadium Audio System for Music This study investigated subjective and objective parameters of a sound reinforcement system in a large sports stadium (Telstra Stadium, Sydney). The sound at fourteen groups of three receiving positions was studied in an on-site subjective listening test, as well as through objective system measurements. For an orchestral music sample, seventeen system tunings were subjectively assessed with fifteen scales. Objective measurements were made at each receiving position. Results showed significant variation for many of the subjective scales between tunings, as well as between receiving positions. To some extent, subjective and objective measurements were related as they describe system tuning and receiving position. Beyond its specific results, this study highlights a range of difficulties in empirically assessing audio quality for music in a very large venue. This was a Master of Design Science (Audio Design) honours dissertation by Scott Willsallen Publication S. Willsallen and D. Cabrera (2004) "Assessment of music audio quality in a sports stadium," 117th Audio Engineering Society Convention, San Francisco, USA

Acoustic Scattering of Fractal Diffusors This project investigated the sound scattering properties of fractal surfaces based on Koch s snowflake. Surfaces were made from laser-cut perspex (20 mm thick). Acoustic measurements were made in a 2- dimensional space between reflecting planes, using 37 microphones. Results show that the fractal diffusers have a more even diffusion spectrum than an eliptic diffusor of equivalent dimensions, but that the eliptic diffusor achieves greater diffusion coefficients at high frequencies. Increasing the fractal order yields a more even diffusion spectrum. David Degos and Steve Edson worked on this project as part of their Master of Design Science (Audio Design). Publication D. Degos, S. Edson and D. Cabrera (2006) "Koch's snowflake: a case study of sound scattering of fractal surfaces," 120th Audio Engineering Society Convention, Paris, France

This study involved a survey of the acoustic conditions in historic cinemas in New South Wales. In some cases there were substantial deviations from modern cinema acoustic recommendations. Galleries, which are both common and popular in historic cinemas, pose significant acoustic challenges including (i) maintaining acoustic clarity in the gallery, (ii) maintaining sufficient sound under the gallery, and (iii) avoiding problem reflections from the face of the gallery. Kamani Koralage Master of Design Science (Audio Design) Dissertation K. Koralage and D. Cabrera (2003) "Historic cinema acoustics," Australian and New Zealand Architectural Science Association Conference, Sydney, Australia 337-352 Acoustics of Historic Cinemas

Acoustical Measurements at the Sydney Opera House A large number of acoustical measurements have been made by the Audio and Acoustics research group in the Sydney Opera House s two large auditoria for a variety of research projects, for example: * Spatial characteristics of auditorium sound-fields * Stage acoustics for opera singers * Subjective spatial impression of auditoria * Archival acoustics and sound-field simulation * Individualisation of head-related transfer functions S. Ternström, D. Cabrera and P. Davis (2005) "Self-to-other ratios measured in an opera chorus in performance," Journal of the Acoustical Society of America 118(6), 3903-3911 D. Cabrera (2005) "Reproduction of room sound-fields for subjective assessment," Australian Acoustical Society Conference, Busselton, Australi J. Y. Jeon, S. Y. Kim, D. Cabrera and J. Bassett (2005) "The effect of visual input on the evaluation of the acoustics in an opera house," Forum Acusticum, Budapest, Hungary A. Nguyen and D. Cabrera (2004) "Visual counterparts to spatial impression in auditorium acoustics," International Symposium on Room Acoustics: Design and Science, Awaji Island, Japan J. Bassett, C. Jin, D. Cabrera and R. Osman (2004) "Measuring the directional variation of spectral energy across time in the Sydney Opera House," International Congress on Acoustics, Kyoto, Japan A. Nguyen and D. Cabrera (2004) "Auditory and visual spatial impression: Recent studies of three auditoria," 148th Meeting of the Acoustical Society of America, San Diego, USA (invited paper, abstract only) J. Bassett, R. Osman, Y.-J. Choi, and D. Cabrera (2003) "A means of documenting the acoustic quality of spaces," Australian and New Zealand Architectural Science Association Conference, Sydney, Australia, 104-116

Auditory Vertical Localization This series of studies investigated how sound source elevation and sound signal characteristics affect the perceived elevation of the sound. Results consistently show that high frequency sound tends to be perceived to come from higher in space than low frequency sound. This has been tested with band-limited noise, complex tones and recorded music; for sources in front of and to the side of the listener; and for single stimuli and simultaneously presented pairs of stimuli. One possible application of this is in loudspeaker design, in the vertical arrangement of tweeter and woofer drivers. Sony scholarship holders Steven Tilley and Sam Ferguson did honours dissertations on this as part of their Master of Design Science (Audio Design). Dr Densil Cabrera also studied this as a visiting scholar at Kobe University, Japan. D. Cabrera, M. Morimoto, K. Sakagami and H. Sato (2006) "Potential low frequency environmental cues for sound source elevation," 9th Western Pacific Acoustics Conference, Seoul, Korea (invited paper) D. Cabrera, S. Ferguson, S. Tilley and M. Morimoto (2005) "Recent studies on the effect of signal frequency on auditory vertical localization," 11th International Conference on Auditory Display, Limerick, Ireland S. Ferguson and D. Cabrera (2005) "Vertical localization of sound from multiway loudspeakers," Journal of the Audio Engineering Society 53(3), 163-173 S. Ferguson and D. Cabrera (2004) "Simultaneous vertical localization of low- and high-frequency noise bands," International Congress on Acoustics, Kyoto, Japan D. Cabrera and S. Tilley (2003) "Vertical localization and image size effects in loudspeaker reproduction," 24th Audio Engineering Society Conference on Multichannel Audio, Banff, Canada D. Cabrera and S. Tilley (2003) "Parameters for auditory display of height and size," 9th International Conference on Auditory Display, Boston, USA, 29-32 Photographs of everyday acoustic environments tested as part of this project in Kobe, Japan

Auditory Alerts for Air Traffic Control Consoles Commissioned by Airservices Australia, this project developed a set of auditory alerts for air traffic control consoles used throughout Australia. Alerts were designed to represent intuitively the urgency of the event, using signal parameters such as pulse rate, number of pulses in a group, pause between group repetition, and tone fundamental frequency. Effort was also made to make the alerts maximally localizable, so that the console with the alert event could be identified quickly. Other considerations included: maintaining audibility in a work environment with variable ambient noise; maintaining a low stress work environment; avoiding speech interference; and minimizing the number of auditory alerts sounded. The alerts were implemented throughout Australia in July 2005. The project was conducted by Dr Densil Cabrera and Sam Ferguson (PhD student in Audio and Acoustics) Spectrographic representation of the hierarchical auditory alerts Background noise in air traffic control centres D. Cabrera, S. Ferguson and G. Laing (2006) "Considerations arising from the development of auditory alerts for air traffic control consoles," 12th International Conference on Auditory Display, London, Great Britain D. Cabrera, S. Ferguson and G. Laing (2005) "Development of auditory alerts for air traffic control consoles," 119th Audio Engineering Society Convention, New York, USA