A high-quality acoustic system that could be used to improve non-invasive ultrasonic imaging and sensing is part of world-first research by an international team led by UNSW Canberra.

‘Sound Trapping in an Open Resonator’ published today in Nature Communication, explains how acoustic energy at a single frequency could transform acoustic sensing and imaging technology. This technology is used in a range of fields including biomedicine and defence.

Lead author Dr Lujun Huang said the aim of the study was to discover the physical structure behind existing acoustic confinement devices and develop a world first high-quality-factor resonant confinement structure.

“High-Q relates to the quality of resonance, so the higher the Q-factor at the resonant frequency, the longer the excited mode can be sustained. The purity of the mode can lead to more accurate sensing,” Dr Huang said.

“The extreme acoustic energy confinement that we have demonstrated first has far-reaching implications for existing sound-based acoustic structures that can be used in ultrasonic biomedicine, sound lasers and high-resolution sensing.

“This is the first time that such a high-Q factor resonance has been experimentally demonstrated in research, as previous research so far has been focused on limited Q-factor acoustic resonances for broadband application… as opposed to our narrowband approach.”

Optical image of acoustic devices and setting up for experimental measurement.

Attaining a high-Q factor can help confine sound-based devices' acoustic energy at a single wavelength, as a single frequency.

This high-Q factor resonance is characterised by a sharp peak in the acoustic reflection or transmission spectrum.

The resonance created from this approach can then be used as an energy concentrator on existing systems, resulting in more targeted sound laser technology and better high-resolution imagery that uses a non-invasive sound-based approach.

Fellow researcher Dr Yan Kei Chiang said a high-Q factor can assist with the confinement of the acoustic energy at a single wavelength, as a single frequency. Therefore, the resonator can then be used as an amplifier.

“So, let’s say we have something small like an acoustic source, then we can use the resonator that we have demonstrated in this paper as the amplifier to realise a highly collimated acoustic source,” Dr Chiang said.

“Our research streamlines previous sound-trapping arrays that are generally more expensive. We now have a more streamlined approach that replaces very complicated methods.”

The international team also included Mr Fu Deng, Dr David Powell and Professor Andrey E Miroshnichenko from UNSW Canberra; Mr Sibo Huang, Mr Bin Jia, Ms Yi Cheng and Professor Yong Li from Tongji University in China; and Professor Chen Shen from Rowan University in the United States.