Spatial Audio and Acoustics Lab

The anechoic room is highly sound-absorptive (a room with ‘no echoes’). It is also vibrationally and acoustically isolated from the building, and has a quiet air conditioning system, yielding a background noise level below the human hearing threshold. The anechoic room is used for precise measurement of sound sources (such as loudspeakers, musicians or noise-making appliances), including measurements of sound source directivity. A sound recording made in the room captures the source alone, without any of the normal contribution of room acoustics.

Features of the anechoic room include:

• anechoic lining that uses a graded density design (thickness of 430mm)
• lining designed by Dr Jingfeng Xu during his PhD at Sydney
• an anechoic low cut-off frequency of 200 Hz
• highly sound-absorptive below 200 Hz
• dimensions between the faces of the lining are 6.5m x 3.6m x 3m (height).

The room is also used to study sound propagation (eg reflections, scattering and diffraction) and it’s possible to add a hard sound-reflective floor to temporarily make the room hemi-anechoic. We also use the room for subjective testing (listening tests), when a very quiet or acoustically controlled environment is needed. We also developed a room acoustics auralization system for voice, for use in the anechoic room. This has been used to study the acoustical quality of rooms for singers and performers. 

A reverberant room is the opposite of an anechoic room: this room has a very long reverberation time for its size, achieved by using surfaces that absorb very little sound. The main purposes of the reverberant room are to measure sound absorption coefficients of surfaces and materials, the power level of sound sources, and sound insulation of lightweight building elements. The build-up of sound in a reverberant room enables the generation of high sound pressure levels, while the long reverberation time creates a diffuse sound field (aided by acoustic reflectors). This allows the sound field to be understood statistically and makes measurement of sound absorption or power very efficient, compared to equivalent measurements in an anechoic room.

Features of the reverberant room include:

• 6.35m x 5.1m x 4m (height)
• constructed from concrete and rendered masonry
• chains from the ceiling used to support sound diffusing panels
• an opening for testing the sound insulation of lightweight building elements such as glazing.

The laboratory also houses a 1:6 scale model reverberant room, which is primarily used for measuring the acoustic scattering of physical scale model surfaces.

Completed in 2015, this facility, also referred to as ‘the dome’, consists of 196 independent small loudspeakers arranged over a hemisphere, in a sound-absorptive room. Features of the dome include:

• an array radius of approximately 2.4m
• a mean interval between adjacent loudspeakers of 11.5 degrees
• a raised platform which positions a single listener, or equipment, at the focus of the loudspeaker array
• multiple microphones and position-tracking equipment
• automatic measurement, yielding large arrays of impulse responses.

The dome is used for:

• auralisation of acoustic environments (creating realistic simulations for listening experiments)
• research in spatial hearing (measuring individualised head-related transfer functions, and presenting stimuli for spatial hearing experiments)
• research in spatial audio rendering (testing and developing rendering algorithms)
• creative audio production using a very high degree of spatial control
• measuring the spatial distribution of reflected sound fields from surfaces (to measure scattering, diffusion, directional absorption and retroreflectivity).

We have a substantial amount of equipment for measurement of architectural surfaces and materials. This includes equipment for measurement of airflow resistivity, acoustic impedance and acoustic scattering, which supports the design of new acoustic surface treatments. The laboratory also holds extensive equipment for field measurements in buildings. This supports investigations into room acoustics, airborne and impact sound insulation, speech intelligibility, and audio system performance.

In recent years, large-scale field measurement projects have been conducted on auditorium stage acoustics and open-plan office acoustics.

The audio studio includes a production room and a recording suite. The production room is 9.2m x 5.5m, with a ceiling height of 3.8m, and includes overhead and surrounding loudspeakers (a 32-channel loudspeaker system is used together with a conventional 5.1 system). The production room is used for audio production projects and as a specialist classroom for audio teaching. The recording rooms are relatively dry acoustic spaces, allowing recordings to be made with some acoustic support.

We perform Normal Incidence Material Testing in our Bruel & Kjaer 4206 Impedance Tube Kit to determine the absorption and overall noise reduction coefficients. Please refer to this excerpt of the 4206 manual for sample size specifications.

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The Bruel & Kjaer Sound Level Meter Type 2250 is a single-channel hand-held analyzer and sound level meter. It is designed for sound and vibration measurements, analysis and recording applications. Installed Applications:

• BZ – 7222: Sound Level Meter
• BZ – 7223: Frequency Analysis
• BZ – 7224: Logging
• BZ – 7226: Sound Recording
• BZ – 7227: Reverberation Time
  

Calibrator included in hire.

$300 per day + GST

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The Bruel & Kjaer Tapping Machine Type 3207 is an impact sound generator. It can be used for impact sound measurements to national and international standards.

$200 per day + GST

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