To do this a small "reflector" is fixed to the probe – the size is around 5mm diameter x 1mm thick.
探针上固定了一个小的“反射镜”——大小大约为直径5毫米，厚度1毫米。
2
Other researchers have built similar devices in the past, but they always required a precise setup where the sound source and reflector were at fixed "resonant" distances.
过去一些研究人员也做过类似的装置，但在事先总是需要精确设定确保声源和反射器在固定的“共振”距离。
3
The new device shows that it is possible to build a "non-resonant" levitation device — one that does not require a fixed separation distance between the source and the reflector.