Acoustic Monitoring Technology Development

@ Galway Bay Marine Renewable Energy Test

Paul Gaughan(Marine Institute - Ocean Energy Development Team) / Declan Murray (P&0 Maritime)

Galway Bay Acoustic Project Concept and Aims

• Establish a permanent acoustic evaluation test facility at the Spiddal ¼ scale energy test site in Galway Bay

• First Renewable energy test site in the world to have this [standing] capability –to characterise WECs in whilst testing

• Provide comprehensive and rapid device characterization and longer term operational monitoring for performance assessment and design feedback for WECs in various sea states

• Develop Irish leadership and ecosystem development in acoustic technology.

• Develop Acoustic Monitoring Research Project findings (technology and methodology)

• Common and open standards-based ICT infrastructure that is flexible, extensible, and serves varied stakeholders/users

• Utilise new subsea cable system for power and communications for acoustic technology development

• Develop 3 Acoustic Systems - Mobile Low power Buoy system, Multi-Channel Acoustic Array , iCListen Cabled Hydrophone

• An OceanSonics iCListen hydrophone has been deployed on the

cabled observatory infrastructure since July 2015

• sensitive broadband digital hydrophone. It is a compact, all-in-one

instrument capable of processing data while collecting in real-

time.

• wave form data collected by the hydrophone processed to a

summary file by a Fast Fourier Transform.

• issues with electrical noise and interference from instrumentation

which are affecting its performance at high frequencies

• icListen generates FFT data in Ascii text format as well as raw

*.WAV files which are recorded in real-time with the bespoke

ICListen data acquisition software tool called “Lucy”.

• spectrograms can be produced with the software allowing detailed

analysis of the acoustic dataset

• All Wav files and FFT are available on smartbay.marine.ie

• Live audio available online via Spiddal.marine.ie/sounds/

ICListen Hydrophone HF Acoustic System

• Partership with sister EMSO observatory “Obsea” in Spain/Catalonia

• Publish acoustic data relevant to MSFD requirements onto EMODNET Physics Portal

• Each provider will provide at least the following:• SPL in dBRMS re 1 µPa with 20 seconds of integration

time• SPL63 in dB re 1 µPa at 63 Hz with 20 seconds of time

integration• SPL125 in dB re 1 µPa at 125 Hz with 20 seconds of time

integration• Hydrophone metadata

• Sampling frequency • Antialiasing filters applied• Gain• Sensitivity• Offset, in counts if it’s possible

Standardisation of Acoustic monitoring through collaboration

• Lucy is a PC program to view and interact with data collected by icListen Smart Hydrophones.

• Lucy displays real-time waterfall and time-series data. Lucy’s waterfall display lets you make accurate measurements from recorded or live data

• The predominant noise (big grey markers) is up at 160 kHz are related to the switching frequency of the DC power supply.

• Three of the four grey markers on the left are at 40kHz, 80 kHz and 120 kHz which are harmonics of the 160 kHz noise.

• Spectogram plot (frequency vs intensity) shows the noise floor of the system is 57 dB at frequencies above 30 kHz and rises to circa 80 dB at low frequencies. The red and purple markers indicate the kind of noise expected at the site with a ‘clean’ power supply

Spectogram from the iCListen hydrophone during testing for electrical noise and interference from the Cable End Equipment in Galway Bay July 2017

iCListen Data Analysis

Pre-

AmplifierFilters

A/Digital

converter

PC based

Omiga

software

PC based

“Lucy”

iCListen

software

Analog Hydrophone/PV

Buoy and Array Systems.

ICListen Smart

Hydrophone

Low Power Mobile Acoustic buoy

• Built on a Mobilis DB8000 platform

• GeoSpectrum M20 Particle Velocity Sensor (PVS) and a Geospectrum M8E hydrophone are mounted on a bespoke, stainless steel, tetrahedral, seabed lander. Both acoustic sensors are connected to a surface platform via an umbilical cable

• Surface platform houses the system’s electronic components and includes an Analogue to Digital Converter (ADC) to convert the raw analogue audio data from the sensor platform to digital format, operating at up to 500k samples/sec at a resolution of 16 bits.

• Transmission to the base station is achieved via point-to-point microwave-radio link.

• Platform is powered via a highly developed solar photovoltaic array +wind power and storage capability in the form of a battery

Data Acquisition Link via CEE

Subsea Enclosure

Lander

Lander

Lander Lander

Lander

Lander

Particle Velocity Detector

Hydrophone

Schematic of the sub-sea acoustics array design with 6 landers linked to subsea enclosure which is connected to the Spiddal Subsea Instrument Node with 2 hydrophones and 1 PVD per Lander

• Built on a lander platform that rest on the seabed and is comprised of a number of integrated sub-systems.

• made up of six bespoke, stainless steel tetrahedral seabed lander sensor platforms,

• mounted with a Geospectrum M20 Particle velocity sensor and securing a pair of Geospectrum M8E hydrophones at different heights in the water column with the second hydrophone providing redundancy.

• landers are connected to an individual Analogue to Digital Converter (ADC) unit which are housed in a single bespoke subsea enclosure along with the controller and supporting electronics.

• 100m hybrid power /fibre-optic cable connects system to the undersea cable hub, providing power for the array’s electronics and a fibre-optic data link to the shore-based data acquisition platform

• Array receives a 26V 6 amp power supply down converted from the 400v DC from the Galway Bay Cable Scientific Node

• Bespoke Signal acquisition and data streaming system developed by Omigatechnologies on the Labview Software Platform

Subsea Multi-Channel Acoustic array Design

Test Site layout and location

670m x 560m in extent 37.2 Hectares (Total area)

Water depth 21-24m 1.3 km from North Shore

Acoustic SystemAcoustic data

Channels

Daily Data

Output (TB)

Monthly Data

Output (TB)

Low Power Acoustic

Buoy2 .08 2

Subsea Multi-

Channel Acoustic

Array

18 2.0 60

ICListen Hydrophone 1 .04 1.2

Acoustic Data Acquisition and Storage.

• Data Available for download online – searchable by sensor and by data • >60TB Acoustic data Collected and stored• Storage Space an Issue• Long term storage solutions – what is required/feasible• Data Quality and Analysis Gaps need to be addressed

Acoustic Buoy System

• The buoyed system is comprised of a GeoSpectrum M20 particle velocity sensor .

• Geospectrum M8E hydrophone

• Both acoustic sensors are connected to a surface platform with an 80 meter load bearing cable

• Mobilis Data Buoy houses the system’s electronic.

• Transmission is achieved via a 5.6 GHz point-to-point microwave-radio link.

Power System

• The buoy is fitted with 14 * 100W solar panels

Solar MPPT controllers

Battery Bank.

▪ Multichannel analogue to digital converter (ADC).Operating at up to 500k samples/sec at a resolution of 16 bits

• MooringA ‘quiet’ mooring made of dyneema and nylon elements

Problems and changes

• Problems with mooring failures.

• Dyneema failed on a number of occasions due to abrasion

• We changed back to the tried and tested chain.

• Put rope through the links of chain to reduce the noise of the chain

• Noise caused by radio link to shore

• The ADAM module that connects to the PV to read the XYZ of the PV caused a lot noise on the across the spectrum of collected RAW acoustic data.

• We also had a tcp buffer problem

AD with new buffer and local storage

Equipment Inventory

Acoustic Array System

• The array system is made up of six seabed landers.

• Each lander mounted with a PV sensor and securing a pair of hydrophones.

• Each of the six landers are connected to an individual ADC unit along with the controller and supporting electronics.

• A hybrid power / fibre optic cable connects the array system to the Cable End Equipment

Array electronics

OCM array bottle leak test

Hybrid cable that connects Array to CEE. 50 meters

Full array test with all 6 cables connected

Thanks For your Attention !