Harris, P M; Robinson, S P; Wang, Lian (2023) Study of the in-situ calibration of hydroacoustic sensors. NPL Report. AC 24

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Abstract

The Joint Research Project 19ENV03 “Infra-AUV” of the European Metrology Programme for Innovation and Research (EMPIR) [Infra-AUV] has delivered traceable calibration of acoustic, underwater, and seismic sensors for measurements at low frequencies, as well as improved knowledge of their performance in-situ. Various case studies have been used to demonstrate the impact for different end-user communities of that traceability and improved knowledge. As a component to achieving traceability from primary standards to a sensor deployed in the field, the project has investigated methods for the in-situ calibration of a sensor to deliver a calibration curve for the sensor accompanied by uncertainty information.

The objective of the study described in this report is to understand the extent to which a mixture of sources of sound can be used for the in-situ calibration of the hydroacoustic sensors within the International Monitoring System (IMS) operated by the Commission for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) [CTBTO]. For this purpose, the approach taken for the in-situ calibration of infrasound sensors described in Gabrielson (2011), Charbit (2015), Green (2021) and Demeyer (2023) is followed, which is based on the application of “Gabrielson’s method”, and extensions to that method, using data recorded by two sensors that are essentially co-located. Simulated data is used to understand the extent to which that method can be applied in the context of hydroacoustic sensors. The advantage of using simulated data is that different aspects of the calibration set-up can be controlled, for example, the distance between the sensors, and how similar are the sensor calibration functions, etc. However, consideration is also given to applying the method to real data gathered by sensors deployed in NPL’s Wraysbury reservoir. A further objective is to implement the approach described in Demeyer (2023) to evaluate the uncertainty associated with the calibration of one sensor considering the other sensor as a reference sensor for which calibration information, comprising a frequency response with associated uncertainties, is available.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	AC 24
Subjects:	Acoustics > Underwater Acoustics
Divisions:	Data Science
Identification number/DOI:	10.47120/npl.AC24
Last Modified:	25 Mar 2024 13:14
URI:	https://eprintspublications.npl.co.uk/id/eprint/9947