Harris, P M; Robinson, S P; Wang, L (2023) A study of uncertainty propagation for an end-to-end data processing pipline for an application in underwater acoustics. NPL Report. AC 25

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Abstract

The data recorded by a sensor operating in the field, possibly as part of a deployed sensor network, are used by different end-user communities for different purposes. For example, in the case of underwater acoustic measurement, the data might be used for event detection and attribution to derive temporal, spatial and amplitude information about the event, which can be anthropogenic or natural. Another use might be for ocean noise monitoring in which the data are used to derive metrics for ambient noise maps for a given spatial region and time period, for example, the percentage of time that an exposure threshold for sound pressure level is exceeded. Yet another use might be for environmental monitoring in which the data are used to derive long-term (e.g., decadal) trends in sound pressure level and to correlate characteristics of the recorded sound with natural and anthropogenic sound sources.

The Joint Research Project 19ENV03 “Infra-AUV” of the European Metrology Programme for Innovation and Research (EMPIR) [1] 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. Specifically, the project has investigated methods for the propagation of uncertainty, including that associated with the calibration of a sensor, through models for high-level derived parameters related to various end-user applications. Quantifying reliably the uncertainty for estimates of these high-level parameters is essential when those estimates are used for decision-making or to inform policy, as well as to understand the comparability and consistency of estimates relating to different locations and times.

The objective of the study described in this report is to investigate the propagation of uncertainty through models related to a particular end user application, viz., a study of the data provided by acoustic sensors at the hydroacoustic stations that form part of the International Monitoring System operated by the Commission for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) [2]. Each hydroacoustic station consists of three acoustic sensors placed in the deep ocean sound channel where the vertical sound speed profile exhibits a minimum. The locations of the stations allow good spatial coverage of the world’s oceans by taking advantage of the physical principles governing the propagation of sound in water. The sampling frequency for the sound pressure recordings is 250 Hz to provide information at acoustic frequencies up to 100 Hz, and a bit depth of 24 bits yields a maximum possible dynamic range of approximately 144 dB. Data is available over periods of years, and at some stations for periods in excess of ten years. Although the primary aim of the data is to support the monitoring of the Comprehensive Nuclear Test Ban Treaty, it is also made available by to support environmental research and, consequently, is used by users in many other and diverse applications.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	AC 25
Subjects:	Acoustics > Underwater Acoustics
Divisions:	Data Science
Identification number/DOI:	10.47120/npl.AC25
Last Modified:	25 Mar 2024 11:26
URI:	https://eprintspublications.npl.co.uk/id/eprint/9946