All-Optical, Air-Coupled Ultrasonic Detection of Low-Pressure Gas Leaks and Observation of Jet Tones in the MHz Range.We used an ultrasensitive, broadband optomechanical ultrasound sensor to study the acoustic signals produced by pressurized nitrogen escaping from a variety of small syringes. 
optomechanical ultrasound sensor
These observations are made possible by the broadband, ultrasensitive response (for air-coupled ultrasound) of our optomechanical devices. 
optomechanical devices