A Metrology Technique for Airborne Ultrasound in Occupational Health Based on High Spatial Resolution Scans at a Reference Workplace

Ultrasound techniques have found a growing number of applications in many fields of industry. The risk assessment of a worker's exposure to airborne ultrasound emitted by these machines lacks on reliable measurement devices and metrology techniques. Despite the strong need of a risk assessment based on scientific evidence, up to now, far too little attention has been paid to ultrasonic noise. Against this background, the EU-funded project Ears II Metrology for modern hearing assessment and protecting public health from emerging noise sources was initiated. It aims at developing metrology techniques for the characterization of airborne ultrasound fields at workplaces. To gain a profound understanding of the sound field characteristics by repeatable and reproducible laboratory measurements, a reference workplace was built up in a free-field environment within a multichannel three-axis scanning system. High spatial resolution scans of the airborne sound field of an industrial ultrasound welding machine were achieved. They reveal a complex structure of the sound field consisting of an extended interference pattern and high sound pressure levels. These findings give new insights for specifications of measurement devices and serve as a basis for the development of a metrology technique tailored to the specific characteristics of airborne ultrasound.