Hydrophone data format and reporting requirements for biological measurements

1.Introduction

1.1 Purpose

This document outlines metadata requirements and technical specifications for reporting hydrophone surveys. The goal is to ensure alignment with Equinor requirements and data delivery standards. These standards aim to facilitate robust environmental accounting and reporting, particularly concerning mapping of underwater acoustic parameters and monitoring of vocalizing biological sources.

This document provides a framework to ensure that providers of technological services (also known as the vendor) give a full overview of all relevant parameters needed for understanding, evaluating and post analysis of the data. Further, the procedures and requirements outlined below facilitate how the vendor shall deliver their data to Equinor.

1.2 Scope

Hydrophone data may be generated by stationary or moving hydrophones (e.g. onboard autonomous vehicles or as a towed array). Deployments may also range from single hydrophones, mostly with omnidirectional characteristics to hydrophone arrays where several hydrophones are used to identify the direction of a received acoustic signal. A single hydrophone will create single channel data, whilst arrays can create multi-channel data where the channels are time synchronized.

The scope ensures alignment with international and regional regulations while providing flexibility to accommodate project-specific needs.

1.3 Target audience

The intended audience for this document includes external:

• Vendors:  Such as survey providers tasked with data collection and delivery.

• Marine Biologists and Ecologists:  Professionals responsible for processing acoustic data for e.g. classifying species.

• Data technical teams: Data technical teams to implement the data validation according to the standards defined.

2. Delivery of data procedure – step by step

To successfully deliver data to Equinor the following high-level sequence must be followed, and the vendor should be familiar with the requirements outlined in this document.

1. Vendor shares details about their designated data loader and survey (section 3).

2. Equinor supplies a detailed data loading guide to the data loader and informs the vendor when data delivery can commence.

3. The vendor prepares the survey data in conformance with the requirements in this document and the data loading guide (herein, user guide). Any contract specific requirements will be in addition to this.

4. The vendor should ensure all files are valid, readable and comply with format specifications and metadata requirements before delivery. Equinor’s automated ingestion mechanism will validate several aspects of the data being delivered. Failures will result in retransmittal requests.

5. When the data is prepared, the vendor shall inform Equinor that data loading is commencing and begin delivering the data.

3. Requirements about data loader and survey

The vendor needs to supply all the “survey related” information in table 1 prior to data delivery. The data loader’s email address and phone number will be used as their main identifier in Equinor’s systems. Equinor requires that email addresses are used solely by the data loader (i.e. it is not a shared email account).

Once a Equinor have given the go-ahead (see section 2 above), the data loader may proceed with the subsequent data upload. When loading data please follow the instructions in the separate user guide .

The vendor shall return the information described in Table 1 via email to Equinor contact person described in contract.

Table 1: Information required before initiating data upload

Required metadata	Data Type	Description	Example
Vendor Support email address	Text	Email address where Equinor can address technical questions to vendor	support@vendor.com
Data loader email address	Text	A person in vendor organisation who will deliver the data to Equinor. Otherwise known as “Affiliate user”	A_Data_Loader@vendor.com
Data loader mobile telephone number	Number	Telephone number of vendor who will deliver the data. A SMS will be sent for confirmation of authenticity	(country-code) 12 34 56 78
Vendor name	Text	The company responsible for acquiring the data.	Jasco
Survey start Date	Date   (YYYY-MM-DD)	The date of survey activity started	2024-01-15
Survey centre point	Latitude, longitude of centre point of survey Decimal degrees (8 digits)	A single location representing the centre of the survey	59.12345612,10.65432123
Survey vessel name	Text	The name of the vessel which acquired the data	The name of the vessel used
Station names and positions	Comma separated text stationA_name, latitude,longitude,stationB_name,latitude, longitude,	Please supply Equinor with a comma separated list of names and lat/long of each station where data was acquired. If the station is on a moving platform like a vessel then please supply the position at the commencement of data acquisition The station naming convention should be consistent with reports and other documentation supplied by the vendor	Hywind, 59.12345612, 10.65432123, Tampen, 59.12345662, 10.65432133

4. Metadata delivery

Metadata plays a pivotal role in ensuring the consistency, traceability, and usability of data collected during surveys gathering acoustic material for characterisation of ambient noise parameters and biological measurements. It serves as the backbone for data integration, regulatory compliance and effective environmental analysis. This section outlines how metadata shall be delivered and the core metadata categories necessary to support these objectives, which include fields necessary for survey documentation, including survey-specific and geospatial metadata.

Metadata shall, if no other requirements are given, be delivered to the following folder “DataAcquisitionInformation” (see section 5)

The metadata requirements are grouped into the following categories

I. Survey Metadata (see section 4.1): Captures details about the overall survey context, effort, and temporal information. Equinor requires that all data can be accurately located back to where it was acquired and can reconstruct what geographical areas the audio files relate to. In this context, geospatial metadata equates to navigational logs and hydrophone deployment logs for each hydrophone or array over the entire course of a survey. Hence, the vendor shall deliver the position of the audio material.

II. Sensor Metadata (see section 4.2): Documents the technical details of sensors and equipment used during the survey, such as sensor type, calibration, operational parameters, and sample rate.

In the subsequent sections, each metadata category is detailed with specific field descriptions, formats, and validation requirements to provide a comprehensive framework for documenting and delivering survey data.

4.1 Survey metadata

Survey information not already provided shall also be included. This shall refer to the type of survey conducted, consistent with the information provided in Table 1.

All geospatial data is to be delivered in lat/long in WGS84(EPSG4326) datum. All time stamp data should be supplied with UTC time zone and in ISO 8601 format

For naming conventions see section 5.1.

Table 2. Data fields required for delivery of survey metadata

Field	Data Type	Description	Example
Project/Asset Name	Text	Name of project or asset	Hywind Tampen
Location ID	Text	Identifier for survey location	Hywind Tampen_LOC_001
Event ID	Text	Unique ID for survey event, e.g. survey transect, station	Hywind Tampen_LOC_Ev001
Survey Start Date and Time	Date   (YYYY-MM-DD HH-mm-ss)	Start date of survey activity	2024-01-15
Survey End Date and Time	Date   (YYYY-MM-DD HH-mm-ss)	End date of survey activity	2024-06-15
Vessel name	Text	Vessel used for deployment	Titanic
Sensor platform	Text	Platform carrying the sensor	If relevant. E.g., type of AUV, lander
Number of stationary hydrophones	Number	1	If relevant
Number of mobile hydrophones	Number	0	If relevant
Latitude *	Decimal (8 digits)	Latitude in decimal degrees	59.12345612
Longitude *	Decimal (8 digits)	Longitude in decimal degrees	10.65432123
Deployment depth	Decimal (2 digits)	Depth of hydrophone. If not applicable, use average depth of surveyed area	200.45

*For moving systems, e.g. AUVs, the vendor shall provide the coordinates for a bounding box with minimum and maximum values of latitude and longitude in decimal degrees (WGS84(EPSG4326)) for the entire survey area. Details of the navigation information shall be implemented in accordance with section 5.1.3.

Validation/check list:

• Ensure all coordinates fall within the operational survey area.

• Verify datum consistency across all survey data.

• Verify time zone consistency across all survey data

4.2 Sensor metadata

Sensor metadata describes the equipment used during the survey, ensuring transparency and reproducibility of data collection. The vendor shall document the type of system used and all relevant settings of the recording device. Note: If more than one type of sensor is used then then this information should be supplied for all the different types of sensors deployed.

Table 3. Sensor metadata.

Field	Data Type	Description	Example
Hydrophone model	Text	Brand of recorder	BigEar2000
Hydrophone frequency range	Number	Range between low and high frequency in between the hydrophone output is linear. Units in Hertz	5 to 20000
Hydrophone firmware	Text	Firmware version
Storage capacity	Text	Storage system and backup configuration	SD card
Sensor output	Text	Describes acoustic output format	WAV
Sensor sample rate	Number	Sample rate. Units in Hertz	48 000
Sensor bit depth	Number	Bit depth	24
Sensor duty cycle	Text	Continuous vs duty cycled dataset	10 minutes on, 50 minutes off
Sensor calibration	Number	Standard factory calibration consists of a piston phone calibration, performed for different gain settings. The calibration data shall be provided as an end-to-end value or as sensitivity described in voltage terms Date of calibration (YYYY-MM-DD)	e.g., - 173 dB re 1µPa 2025-01-10
Preamplifier gain	Number	Fixed gain settings and additional modifications	-4 dB
Data compression	Text	If applied, describe the algorithm and quality settings.

4.2.1 Acoustic calibration:

The .wav file is assumed to be normalised with ±1 values and a full signal scale of 2 units peak to peak, or as integer, e.g. from -32000 or +32000. The calibration data shall be provided as an end-to-end value allowing the .wav files to be displayed as calibrated SPL in dB re 1µPa or as absolute values in µPa.

Information relevant on calibration of .wav must also be added to the header of the .wav file to ensure each.wav file is self-explaining to avoid data loss during the process of data usage and sharing. This is of particular importance with regards to the sampling rate and the calibration factor. The standard header of the .wav files must be used, and additional lines should be added for the end-to-end calibration.

Please note that we require a double description of the calibration. The general way how the system and the hydrophones are calibrated must be part of the final report. However, each .wav file shall also include information on calibration, e.g. by adding information in the header. It is not acceptable if only proprietary software can be used to use the .wav files with calibrated values.

Validation/check list:

• Validate sensor data against operational requirements (e.g., altitude and heading accuracy).

• Ensure metadata overlays (e.g., timestamp, location) in video and image files.

• Ensure that Calibrated .wav files are delivered on a format enabling use of open software

5. Data formats and delivery location

This section summarizes data format and file naming requirements for deliveries of hydrophone data. The objective is to give clear instructions to enable automated ingestion.

The nomenclature for biology shall be reported in accordance with Catalogue of Life, and, if relevant, in accordance with other country specific requirements. Surveys carried out under these requirements must agree to standard techniques and/or perform intercalibrations among techniques or observations to ensure comparability in the results. 

If the vendor has problems understanding where to load data, please contact the Equinor contract representative.

5.1 File formats and naming conventions

Raw, pre-processed, processed, and interpreted data shall be kept as separate entities, each with its own storage location. Further, Equinor requires that navigational data originating from moving deployment platforms (e.g., AUVs and vessels) is provided to further contextualize the delivered datasets.

File format:

All data shall be delivered on a machine-readable format using a globally accepted industrial standard relevant for the class of data which enables Equinor to read the file contents using open-source tools.

Requirements regarding time extent:

Date and time period for each file shall relates in the filename and in the report.

5.1.1 General requirements for audio datasets

File format:

.wav, uncompressed, minimum 24-bit sample depth, not resampled

Mandatory file header requirements (these are standard for .wav files):

• Sample rate

• Audio format

• Number of channels (will be greater than 1 if this file contains data from a multiple hydrophones)

• Bits per sample (Equinor require a minimum of 24-bit data)

• Type of processing conducted

Specific requirements regarding audio time extent:

All data in an individual file must be contiguous with respect to time and have the same sample rate. The time period covered by each individual file should be no more than 10 minutes, and each channel in a multichannel file should cover exactly the same time period and begin at the same start time.

File naming convention:

The association between files and their associated parent data (if any) should be explained in the report. Required file naming structure

Stationary:

< Asset/Project >< Contract-number >< Station >_< Timestamp-Of-Start-Of-Data-In-File >.wav

Mobile:

< Asset/Project >< Contract-number >< Timestamp-Of-Start-Of-Data-In-File .wav

Note that is removed and that there is only one '_' (underscore) between and

Where < Timestamp-Of-Start-Of-Data-In-File > is the UTC time and date at which the first data sample in the file was acquired written in this format: YYYY-MM-DDThh : mm:ssZ (eg. 2025-03-25T14:32:00Z).

Storage requirements:

• Raw audio data

  Defined as files containing unadulterated audio waveform data acquired during a survey with no processing, calibration or data cleansing routines applied. Equinor will rarely request this data and if so, it will be made clear in the contract and have special conditions attached (e.g., to comply with data protection regulations).
  Folder to store this type of data: “RawHydrophoneWaveformData”

• Pre-processed audio data

  Defined as quality controlled acoustic waveform data where pre-processing operations have been applied including application of calibration, cleansing to remove erroneous, incorrect or data which does not comply with data protection regulations.
  Folder to store this type of data: “PreprocessedHydrophoneWaveformData”

• Processed audio data

  Defined as quality controlled acoustic waveform data where signal processing has been applied (like resampling, filtering, gain, noise removal).
  Folder to store this type of data: “ProcessedHydrophoneWaveformData”

Other requirements:

The vendor should document what processing has been applied to all acoustic data in their report.

5.1.2 Requirements for interpreted data

Defined as data and results extracted from the audio material. For example, automated acoustic signal detection logs, manual acoustic detection logs, spectral values, transformed data, generated data (e.g., outputs of transmission loss, detection probability), and statistics. The survey findings and interpreted biological and environmental data may be utilized and integrated into international and national databases, such as GBIF (Global Biodiversity Information Facility).

File format:

This data should be delivered and be machine readable using a globally accepted industrial standard format relevant for the class of data which enables Equinor to read the file contents using open-source tools. For acoustic signal detection (e.g., whale calls/vessel passages/airguns/pile driving), the datasets shall include information in the form of detection events in a chronological order. A template for interpreted acoustic data is provided in section 6.2 DT1 and DT2.

Datasets for spectral levels, detection probability, and other analytical datasets (e-g., one-third octave levels) shall follow international standards, ensuring the standards used are defined in the final report (see section 6). Similarly to detection data, these additional datasets shall be machine readable using a globally accepted industrial standard format relevant for the class of data which enables Equinor to read the file contents using open-source tools.

Requirements regarding time extent:

Equinor require that the vendor makes it clear what date and time period each file relates in the filename and in the report

File naming convention:

The association between files and their associated parent data (if any) should be explained in the report. Required file naming structure

< Asset/Project >< Contract-number >< Station >_< Timestamp-Of-Start-Date >.csv

Where < Timestamp-Of-Start-Of-Data-In-File > is the UTC time and date at which the first data sample in the file was acquired written in this format: YYYY-MM-DDThh : mm:ssZ (eg. 2025-03-25T14:32:00Z).

Vendor shall choose file names which allow the purpose of the file to be understood linking to explanations in the report.

Other requirements:

The vendor shall document how the interpretations have been made in their report.

Folder to store this type of data: “InterpretedHydrophoneData”

5.1.3 Track data from mobile systems

All datasets originating from mobile systems (e.g., towed arrays or AUVs) shall be provided as navigation logs for the platform. These logs must include a time stamp (in UTC) and geographic coordinates (latitude, longitude in WGS84(EPSG4326)) in decimal degrees at a one-minute resolution. Further, the track data must be synchronized in time with the time stamps provided for the audio files (and hence, the sensor metadata). When applicable, depth profiles shall also be included.

Mandatory file header requirements:

• DateTime (YYYY-mm-dd HH:MM:SS)

• Latitude (decimal degrees)

• Longitude (decimal degrees)

• Depth (m)

File naming convention:

Please provide a systematic overview of the sampling track, including depth profiles when available. Required file naming structure

< Asset/Project >< Contract-number >< Station >< Timestamp-Of-Start-Date >< Latitude >< Longitude>< depth >.csv

If depth profiles are not part of the survey, please fill with NA.

Folder (where to store this type of data): “DataAcquisitionInformation”

5.1.4 Additional data

If relevant, Vendor shall supply additional data when they exist in relation to the respective Scope of Work (SoW). For instance, files whose sole purpose is to relate to the environment the acoustic data was acquired in. Examples include: Metocean data, wind, tide, weather data, operational data from facilities or construction, vessel data, oceanographic data from probes or sensors, biological, geoscientific data. If the vendor is able to provide such additional datasets, Equinor requests that they add a list with relevant metadata associated with the additional instrumentation used in the survey.

File naming convention:

Please provide file names which allows the purpose of the files to be understood so that we Equinor can link these files to the other data they relate to. The association between files and their associated parent data (if any) should be explained in the report. As an example, < Asset/Project >< Contract-number >< Station >< Timestamp-Of-Start-Date >< CTD >.csv

Folder (where to store this type of data): “EnvironmentalRelatedInformation”

6. Reports and supporting information

All reports including preliminary and final reports and the files which support the reports like images, video footage, spreadsheets and audio clips. Photographic documentation of the deployment setup and the equipment on site shall also be provided.

File format:

Industry standard document formats such as PDF and all Microsoft Office 365 compatible document formats. Image files should be provided in industry standard formats such as .jpg, .png for images, mpeg4 for video footage, .wav, mp3 for audio clips.

File naming convention:

Reports should be dated contain the survey name in their file name. Reports should have version number with the final version clearly identified. The association between files and their associated parent data (if any) should be explained in the report.

Other requirements:

Reports should cover all aspects of the work undertaken by the vendor in fulfilment of the contract.

Folder (where to store this type of data): “ReportsAndSupportingInformation”

6.1 Acoustic data report

An acoustic data report shall provide an overview of the data acquisition, survey effort, and main findings, with a description of the analysis’s methods and annotations of relevant acoustic events. The report shall follow accepted scientific practices, where the vendor shall also expand on any known interruptions or gaps in the data.

Further, when automated detectors are used for interpreting acoustic data, the precision and recall of the detectors is explicitly disclosed in the final reporting documents, together with a reference to how these have been calculated. If Artificial Intelligence (AI) detectors are used, the report shall also describe the AI system (e.g., supervised vs unsupervised machine learning), together with quantifiable metrics for its/their performance (e.g., number of samples used for training and validation). Traditional non-machine learning detectors shall also be described.

6.2 Documentation of marine mammal occurrence in time and space

The vendor shall provide standardized documentation of marine mammal detection events, using the following template sheets:

These tables are found here in the following Excel fill that is to be used for reporting:

GBIF Template

Hydrophone_event_ipt report

Info:Please fill out the template as is, do not remove/add sheets/Columns.

DT1: Sampling events

Field	Description	Example
parentEventID	An identifier for the broader Event that groups this and potentially other Events. E.g., survey ID.	EQ02053
locationID	An identifier for the set of location information. May be a global unique identifier or an identifier specific to the data set.	PAMEast
eventID	An identifier for the set of information associated with an Event (something that occurs at a place and time). May be a global unique identifier or an identifier specific to the data set.	EQ02053_PAMEast
eventStartDateTime	The date-time when the start of the event was recorded. Recommended best practice is to use an encoding scheme, such as ISO 8601:2004(E).	2018-10-05T13:00:00Z
eventEndDateTime	The date-time when the end of the event was recorded. Recommended best practice is to use an encoding scheme, such as ISO 8601:2004(E).	2019-05-26T14:00:00Z
samplingProtocol	The name of, reference to, or description of the method or protocol used during an Event.	Passive acoustic monitoring (PAM)
decimalLatitude	The geographic latitude (in decimal degrees, using the spatial reference system given in geodeticDatum) of the geographic center of a Location.	72.46501
decimalLongitude	The geographic longitude (in decimal degrees, using the spatial reference system given in geodeticDatum) of the geographic center of a Location.	20.34738
geodeticDatum	The ellipsoid, geodetic datum, or spatial reference system (SRS) upon which the geographic coordinates given in decimalLatitude and decimalLongitude are based.	EPSG:4326
countryCode	An identifier for the country where the event occurred. Recommended best practice is to use ISO 3166-1-alpha-2 country codes.	NO
datasetName	The name identifying the dataset from which the record was derived. E.g., contract name.	Johan Castberg Passive Acoustic Monitoring

DT2: Associated Occurrences

Field	Description	Example
eventID	An identifier for the set of information associated with an Event (something that occurs at a place and time). May be a global unique identifier or an identifier specific to the data set.	EQ02053_PAMEast
occurrenceID	An identifier for the Occurrence.	EQ02053_PAMEast_FW_1
basisOfRecord	The specific nature of the data record. Recommended best practice is to use this controlled vocabulary: http://rs.gbif.org/vocabulary/dwc/basis_of_record.xmlLink	MachineObservation
eventStartDateTime	The date-time when the start of the event was recorded. Recommended best practice is to use an encoding scheme, such as ISO 8601:2004(E).	2018-10-05T13:00:00Z
eventEndDateTime	The date-time when the end of the event was recorded. Recommended best practice is to use an encoding scheme, such as ISO 8601:2004(E).	2019-05-26T14:00:00Z
scientificName	The full scientific name. Be as specific as possible.	Balaenoptera physalus
taxonRank	The taxonomic rank of the most specific name in the scientificName.	Species
type	The nature or genre of the resource. E.g., type of call or detector.	Moan detector
occurrenceStatus	A statement about the presence or absence of a Taxon at a Location.	Present
eventRemarks (optional)	Comments or notes about the event.	Anthropogenic noise interference.
organismQuantity (optional)	A number or enumeration value for the quantity of organisms	63
organismQuantityType (optional)	The type of quantification system used for the quantity of organisms. An organismQuantityType must have a corresponding organismQuantity.	% days with acoustic detections

7. Quality assurance

7.1 Compliance

Data shall be delivered in accordance with Chapter 5 & 6. However, if the data does not meet requirements specified in this document, please notify the Equinor contact person specified in the contract. If the hydrophone data meets other requirements than specified in this document, please ensure that all deliverables meet the given regulatory standard(s).

7.2 Data security

All the data supplied shall be encrypted. Sensitive information shall be marked in the dataset, following ownership, confidentiality, and privacy.

8. Glossary

Acronym	Explanation
WGS84(EPSG4326)	World Geodetic System 1984
UTC	Universal Time Coordinator
ISO	International Organization for Standardization
AUV	Autonomous Underwater Vehicle
SPL	Sound Pressure Level
DT	Data Transfer
PDF	Portable Document Format