It’s the room without any echo. Join create on a tour of the anechoic chamber at the UTS Acoustics Lab.
By Lachlan Haycock
The quietest room on earth is surprisingly small.
Strictly speaking, it’s one of the quietest places, rather than the definite example – that record is currently held by a facility in America.
But the tactile, textured dark foam on all four walls and the high ceiling, alongside the muted lighting, stock-still atmosphere and nil echo, create a suitably eerie space.
This is the anechoic chamber at the UTS Acoustics Lab, located in Sydney’s southern suburbs.
Sealed environment
An anechoic chamber suppresses acoustic reflections to replicate free-field conditions – eliminating all reflections, background noise or other aural interruptions.
The UTS Acoustics Lab’s anechoic chamber is one of two main testing rooms at the facility built from concrete and brick. Designed to meet international standards including ISO 26101 and ISO 3745, both achieve a high level of vibration isolation, suspended on arrays of stiff springs and lined with non-flammable foam wedges that extend 900 mm from the walls, ceiling and (in one of the two chambers) floor.
Specially sealed acoustic doors are designed to minimise airborne sound transmission from outside the chamber.
The anechoic chamber contained more than 1300 foam wedges, each 900 mm in length, achieving a cut-off frequency of 89 Hz.
“The bare room dimensions are 6.46 m × 4.66 m × 7.00 m, with a total volume of 211 m³,” said acoustic researchers Qiaoxi Zhu and Benjamin Halkon in a paper submitted to the Acoustics 2025 conference in Joondalup, Western Australia. “The usable space between the wedges and above the wire floor is 4.46 m × 2.66 m × 4.60 m, yielding a usable volume of 55 m³.”
The background noise in the anechoic chamber has been measured at 16.9 dBA, with the bulk of this noise stemming from the sound level meter itself rather than the chamber’s acoustic properties.
“The typical broadband self-generated noise for single-range operation [from the sound level meter in question] is 16.6 dBA, comprising 14.6 dBA from the microphone and 12.4 dBA from electrical components,” Zhu and Halkon said.
Dr Sipei Zhao, Senior Lecturer in Acoustics at the UTS School of Electrical, Mechanical and Biomedical Engineering, told create that the specific shape of the sound absorption materials on the walls and ceilings is intended to absorb soundwaves and reduce impedance mismatch.
“If we have matched impedance, sound will not bounce back immediately from these surfaces, meaning it will propagate inside the material slowly and also be partly absorbed by the material,” he explained.
“The thickness of the insulating foam is dependent on the frequency of the sound wave. Each frequency of sound corresponds to a spacial scale of soundwave. The lower the frequency, the longer the wavelength and the thicker the material we need.”
Some facilities boast an even lower level of background noise than the UTS Tech Lab. An anechoic chamber operated by Microsoft in Washington, USA, has been recognised by Guinness World Records as the world’s quietest room, with a background noise 20 dBA below the threshold of human hearing.
“Most people, when they enter the room for the first time, feel a big difference from the outside environment,” Zhao said. “It feels almost deadly in its silence.
“If you stay in the room long enough, you can hear your own heartbeat.”
In the facility’s hemianechoic chamber, meanwhile – “tailored for acoustic measurements over a fully reflecting plane” on the floor of the chamber, according to Zhu and Halkon – more than 2100 foam wedges extend 900 mm from the walls and ceiling like the anechoic chamber next door.
There is the same cut-off frequency of 89 Hz, but the space is slightly larger, offering bare room dimensions of 9.22 m × 6.90 m × 6.29 m and a total volume of 400 m³. The usable space above the hard floor is 7.22 m × 4.90 m × 5.29 m, yielding a usable volume of 187 m³. The background noise level has been measured at 17.1 dBA.
With its flat floor, the chamber offers even greater testing capabilities, Zhao said.
“In the fully anechoic chamber, we have to stand on metal mesh, because the floor underneath is a special absorbing material. It’s unsafe to place heavy machinery on the metal mesh, so we can use the hemianechoic chamber instead.
“To meet international and national standards for acoustic testing of the noise of equipment and machines, we need a reflective material, or reflective floor, for machinery to sit on.”
Read about the acoustic design of the revitalised Sydney Modern gallery.
Innovation precinct
On the day create visits the UTS Tech Lab, one of the rooms – the hemianechoic chamber – is in use.
A private company, one of many that use the facility, is testing a piece of machinery – but as the research is proprietary, Zhao is suitably tight-lipped as to the project’s nature.
An adjacent space is being used for vibration testing, one of many rooms ringing a vast warehouse full of machining tools, forklifts, saws, gas bottles, meeting rooms and storage areas.
“We recently received an inquiry to test the power of a battery energy storage system,” Zhao said. “That’s very important to do, because as Australian companies upgrade their energy storage systems, they can get quite noisy and often a lot of fans are used to cool down the battery. The company wants to test how much noise is emitted from those fans.”
The UTS Tech Lab is housed in a warehouse not far from like-minded innovative facilities such as Advanced Navigation, forming something of an innovation precinct.
Zhao started his career in electronics engineering at Nanjing University in China, where he conducted an audio engineering project for his Master’s degree. He later moved to Australia to study acoustic engineering in more detail at RMIT.
He’s worked at UTS since 2018, where he is a senior lecturer.
“Acoustic engineering is everywhere. As a research field, it’s a very old subject. The earliest studies in physical science started with acoustics, because we communicate with speech.
“It’s an interdisciplinary study between physical science and electronics engineering, with some signal processing thrown in. Biomedical engineering – with things like ultrasound – underwater acoustics and music are all relevant here. And now the hot topic of AI can also be used to process acoustic information.”
Zhao is one of a small but committed group of engineering and audiologists working in Australia.
The country’s capacity for testing using high-performance anechoic facilities is humble by international standards – and historically limited, with just four such chambers in 2010 and nine as of 2025.
He pointed to the UK as the world leader, with Australia’s reputation on the global stage still rising.
The benefits of acoustic engineering research extend beyond the theoretical to the therapeutic,” Zhao said.
“Noise pollution is becoming a more serious problem, affecting our health and wellbeing. “Some people experience sleep disturbance, for example, from noise. But there aren’t, I think, enough resources devoted to this field. Not enough is done to minimise the impact of noise on the community.
“My hope is that acoustics can be seen as a more important engineering subject, taken into account when designing products or facilities or infrastructure.”
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