Underwater acoustic calibration standards for frequencies below 1 kHz: current status of EMPIR "UNAC-LOW" project

"UNAC-LOW" is an ongoing project under EURAMET's EMPIR programme whose aim is to develop the European metrological capacity in underwater acoustics for the calibration of hydrophones and autonomous noise recording systems for frequencies below 1 kHz. The project will provide an improved framework to underpin the absolute measurement of underwater sound in support of regulation and EU Directives for which traceability is currently lacking. Methods for the calibration of hydrophones and autonomous recording systems in the frequency range from 20 Hz to 1 kHz will be developed and validated by comparison measurements between the project partners. Long-term operation of the calibration capabilities will be ensured by each partner, to provide a coherent metrology strategy for Europe within this field. Current activities regarding the design and preparation of calibration setup are here described, in view of round-robin calibrations and validation scheduled for year 2018.