Underwater AcousticsUnderwater acoustics is a key underpinning technology in offshore oil and gas activities, is increasingly used in oceanographic and environmental studies, and continues to play a crucial role in defence.
The applications of underwater sound span positioning, communications, navigation, echo-sounding, geophysical surveying, water quality measurement, sonar, weapons systems, and tomographic measurements of ocean currents and temperature. Underwater acoustics is a key underpinning technology in offshore oil and gas activities, is increasingly used in oceanographic and environmental studies, and continues to play a crucial role in defence. In addition, the accurate measurement of anthroprogenic noise is key to the assessment of its effect on marine life.
NPL’s underwater acoustics expertise includes:
- provision of primary free-field measurements and dissemination in the frequency range 1 kHz to 1 MHz
- acoustic testing and characterisation of transducers by use of state-of-the-art free-field test facilities consisting of both laboratory tank and open-water sites
- acoustic testing of transducers and materials at simulated ocean conditions by use of the NPL Acoustic Pressure Vessel
- development of standards to meet evolving industry needs, for example in the measurement and assessment of underwater radiated noise
- development of new generation of primary standards by use of optical techniques
- acoustic nearfield methods for sonar characterisation including the use of novel optical scanning techniques
- provision of pressure calibration of hydrophones in the range from 5 Hz to 1 kHz
- Technical Guides on Sound in Air, Ultrasonics and Underwater Acoustics.
- The increasing level of man-made sound in the ocean (whether deliberately generated or not) has led to concern over marine noise pollution.
- Research into a new optically-based primary standard for the calibration of underwater hydrophones for direct and absolute calibration of hydrophones, directly related to the unit of acoustic sound pressure.
- Data describing the variation in performance of commercially available hydrophones with temperature and depth have until now been difficult to obtain and are not readily available from hydrophone manufacturers.
- This shows performance data for a number of commercially available hydrophones that have been characterised at various simulated ocean conditions.
- NPL's Acoustics Pressure Vessel can be used to simulate ocean conditions and support various measurements.
- NPL is currently working on the development of techniques to predict the far-field response from measurements made in the acoustic near-field.
- Details on various underwater acoustics standards, including free-field hydrophone at different frequency ranges.
Underwater Acoustics products & services
Acoustic calibration and testing at simulated ocean conditions (in the NPL Acoustic Pressure Vessel)
The NPL Acoustic Pressure Vessel provides the capability for the free-field acoustic testing of transducers and systems at simulated ocean conditions.- The service offered by this open-water test and calibration facility, based on the reservoir at Wraysbury, near Staines, Middlesex, will be UKAS-accredited for the frequency range 1 kHz to 350 kHz.
- Unique underwater acoustics measurement capability includes two open test tanks that provide a flexible approach to the most demanding testing requirements.
- NPL offers a variety of training courses in underwater acoustic calibration and measurement. Instead of being classroom-based, the courses are "hands-on" – providing experience of real measurements being made with state-of-the-art instrumentation.
- A wide range of consultancy services are available from NPL - these range from advice on specific measurement problems, right through to the provision of complete measurement solutions.
- The NPL Underwater Acoustic Coupler Reciprocity Facility is designed to allow calibrations to be performed at elevated hydrostatic pressures over a range of temperatures.
- A unique suite of underwater acoustics facilities for the calibration of hydrophones and the characterisation of acoustic fields generated by transducers and sonar systems, providing the traceability to national standards for compliance with quality systems.
- In underwater acoustics, accurate measurements are the key to successful product development and high-quality test services.