Calibration standards for hydrophones and autonomous underwater noise recorders for frequencies below 1 kHz: current activities of EMPIR “UNAC-LOW” project


  • Alper Biber TUBITAK MAM
  • Ata Can Korakci TUBITAK MAM
  • Alexander Golick TUBITAK MAM
  • Stephen Robinson National Physical Laboratory
  • Gary Hayman National Physical Laboratory
  • Justin Ablitt National Physical Laboratory
  • Salvador Barrera-Figueroa Dansk Fundamental Metrologi
  • Silvano Buogo CNR-INSEAN - Marine Technology Institute Via di Vallerano 139, 00128 Roma, Italy
  • Salvatore Mauro CNR INSEAN
  • Fabrizio Borsani ISPRA - National Institute for Environmental Protection and Research
  • Salvatore Curcuruto ISPRA - National Institute for Environmental Protection and Research
  • Markus Linné FOI - Totalforsvarets forksningsinstitut
  • Peter Sigray FOI - Totalforsvarets forksningsinstitut
  • Per Davidsson FOI - Totalforsvarets forksningsinstitut



The project entitled “UNderwater Acoustic Calibration standards for frequencies beLOW 1 kHz” (“UNAC-LOW”), currently active within the European Metrology Programme for Innovation and Research (EMPIR), is presented by describing its objectives and current activities. The project aims at developing the metrological capacity of the European Union (EU) for the calibration of hydrophones and autonomous recording systems for the frequency range between 20 Hz and 1 kHz, for which traceability is presently not fully available. In this way, EU metrological capacities for absolute measurement of underwater sound will be improved, with a direct effect on the implementation of regulation and EU Directives that require underwater acoustic measurements to be traceable. After having completed the initial project tasks regarding the review of existing methods and the design of the experimental setups, comparison measurements between the project partners are currently under way and their results will be validated and presented upon project end after first quarter of 2019. To ensure long-term operation of the calibration capabilities by each partner, a coherent EU metrology strategy for underwater acoustics will be developed as one of the main project outcomes. Current activities include the implementation of the calibration setups developed in earlier stages of the project for both hydrophones and autonomous recorders. The methods that shall be used for hydrophones are the pressure method in a closed chamber and the standing wave tube method. For autonomous recorders, in addition to the above methods, calibrations will be performed using free-field methods in different open-water test sites possessing suitable characteristics for low frequency measurements.


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