Paul Lepper | Loughborough University (original) (raw)
Papers by Paul Lepper
The underwater and airborne acoustic environment forms a critical part of many marine mammals lif... more The underwater and airborne acoustic environment forms a critical part of many marine mammals life cycles. Assessment and development of understanding of these acoustic soundscapes is often vital in understanding many marine life and human operation interactions as well as species to species interactions in the natural acoustic environments. Traditional passive acoustic methodologies used for underwater sound and noise measurements include static hydrophones, autonomous loggers, boat-based deployments, towed arrays, drifter systems etc. Most of these systems however also rely on expensive and sometimes hazardous deployments and retrieval methods. The rapid growth in Unmanned Ariel Vehicles (UAV) technologies in recent years has lead to investigation of these platforms to act as enhanced aerial visual platforms for observing marine mammal behaviour, abundance estimation etc. These systems are however often limited by battery life to relatively short in flight deployments. However these platforms can also offer the opportunity for rapid deployment of smart hydrophone systems over a relatively large spatial areas to include acoustic behaviours and sound scape analysis by flying to a site landing on the water and then deploying underwater sensors. Whilst on the waters surface relative power consumption is significantly lower than in-flight allowing significantly longer deployments. Smart systems will then return to some base point with minimal human interaction. A prototype multi-rotor system has been developed and tested in an open water site, capable of flying to site, landing on the water, deploying a wideband hydrophone for underwater noise assessment and then returning to base. Measurements include underwater noise self-noise analysis in-flight, landing, static and take-off and potential implications to marine wildlife. These developments and trials have demonstrated the overall feasibility of wide-scale rapid hydrophone deployment using UAVs for sound field and marine mammal behaviour analysis.
Journal of the Acoustical Society of America, May 1, 2017
Traditional operations such as oil and gas exploration and production have long undergone sound f... more Traditional operations such as oil and gas exploration and production have long undergone sound field and environmental impact assessments of underwater acoustic noise. More recently emerging industries such as renewables (wind, wave, and tidal energy production) have also required scrutiny in terms of underwater noise sound fields. To make these assessments, sound fields are typically measured using hydrophones deployed from boats, drifting systems or moored acoustic data loggers. These measurements are often complex and expensive requiring complicated equipment deployments, boat operations and personnel in often-dangerous or hazardous environments. Unmanned Ariel Vehicles (UAV) or drone based technologies offer the opportunity for rapid deployment of smart hydrophone systems arrays over a large spatial area with significantly lower operator and boat interaction improving deployment flexibility, cost and minimising safety concerns for boat based deployments. Results presented are from tests of a prototype multi-rotor system in an open water site, capable of flying to site, landing on the water, deploying a wideband hydrophone for underwater noise assessment and then returning to base. These developments and trials have demonstrated the overall feasibility of wide-scale rapid hydrophone deployment using UAV based sensors and its potential application to underwater sound field assessment across a variety of industries.
Journal of the Acoustical Society of America, May 1, 2017
Tidal-stream turbines are a promising source of renewable electricity worldwide. These technologi... more Tidal-stream turbines are a promising source of renewable electricity worldwide. These technologies are sufficiently new that only single test devices have been deployed with arrays imminent. Being new, their interactions with marine organisms are poorly understood and the risk of large marine vertebrates colliding with their moving blades is a consenting and ecological concern. Operational noise is also considered a disturbance threat but under what circumstances is poorly defined. Further, the threats of collision and turbine noise may be inversely correlated with animals needing to hear turbines to avoid them. Consequently, there have been proposals to add extra-noise by fitting turbines with acoustic deterrents to warn or scare animals away. In this talk we examine the acoustic interactions between marine mammals and tidal turbines. The interactions are complex and depend on turbine source levels, ambient sound, propagation in moving water, sensory abilities, swim speeds and diving behaviour. In addition, the occurrence of turbines in arrays adds further complexity as responses to one turbine will impact collision risk with another. We then consider the options for and implications of adding additional warning sounds but such quick fixes might have unintended consequences that either increase collision risk or lead to undesirable avoidance.
Journal of the Acoustical Society of America, Oct 1, 2019
The growth of interest in the development of harnessing tidal energy has also led to the requirem... more The growth of interest in the development of harnessing tidal energy has also led to the requirement of assessment of underwaters sound fields in these environments. The radiated acoustic signatures of underwater systems in these environments is of significant interest. The measurements of the sound field in tidal flow areas however offer a number of major challenges. In a high flow environment, a static hydrophone would often suffer from significant flow noise. This parasitic noise is not real in the environment but a result of water column particle interaction with the hydrophone surface and has the capability of severely limiting the systems dynamic range for assessment of the true acoustic environment. Drifting system, moving at the speed of the water flow minimise this by reducing fluid particle to sensor interactions however are constrained by both temporal and spatial variations during the drifting limiting the ability to continuously monitor a system. Flow shield technology (sonar domes) have however been used extensively of the reverse problem of high-quality sound reception from a moving platform essentially suffering from the same problem. Work is presented on the use flow shield concept for a proto-type seabed mounted static recorder deployed in a high flow environment.
Acoustics can provide important information to assess underwater resources, noise and wildlife in... more Acoustics can provide important information to assess underwater resources, noise and wildlife interactions on marine energy sites. The European Marine Energy Centre (EMEC) has collaborated on a number of projects to develop acoustic technology, methods and quality control of monitoring techniques used for such assessments. This paper outlines previous and current activities at EMEC in this area, with a focus upon beneficial advances through knowledge exchange with Loughborough University and other knowledge partners.
This good practice guide was prepared by Stephen Robinson of the National Physical Laboratory wit... more This good practice guide was prepared by Stephen Robinson of the National Physical Laboratory with the assistance of Dr Paul Lepper (Loughborough University) and Dr Richard Hazelwood (R&V Hazelwood Associates). The work to develop new guidance has built upon the expertise already gained by researchers in a number of countries who have been actively engaged in discussions on this topic for some time. It is these informal discussions that have led to the initiation of standardisation work within ISO.
1. ABSTRACT The use of envelope detection methods to reduce the bandwidth of an echolocation clic... more 1. ABSTRACT The use of envelope detection methods to reduce the bandwidth of an echolocation click into the audio-band is not a new concept. However, the increasing popularity of portable digital recorders with excellent signal to noise performance needs such signal processing if ultrasonic transient data needs to be captured. Similarly, this approach allows high frequency information to be recorded onto video recorder sound tracks providing the advantage of synchronised sound with images for behavioural studies. This paper describes the development of a new generation of ECD with improved performance and includes cetacean echolocation data recorded using this equipment in two independent studies.
Conventional underwater based acoustic deployment platforms, such as boats, drifting systems or m... more Conventional underwater based acoustic deployment platforms, such as boats, drifting systems or moored long term acoustic data loggers are often expensive, complex and are usually deployed in dangerous environments. A novel alternative involving the use of a waterproof Unmanned Aerial System (UAS) for the deployment of underwater acoustic sensors is presented. The system has the capability of overcoming the limitations of current deployment methods, while also being able to self-deploy and self-retrieve, and will improve deployment and redeployment times.
A framework to predict, validate and review the acoustic footprints of operating tidal turbines [... more A framework to predict, validate and review the acoustic footprints of operating tidal turbines [abstract]
Environmental dependence of underwater sound propagation resulting from percussive pile driving [... more Environmental dependence of underwater sound propagation resulting from percussive pile driving [abstract]
Pile-driving of marine foundations can radiate substantial levels of low-frequency impulsive nois... more Pile-driving of marine foundations can radiate substantial levels of low-frequency impulsive noise into the water column, which given the right acoustic propagation environment conditions can propagate over large distances. Concern over the potential for impact on marine fauna often results in a regulatory requirement to measure the radiated noise level over distances which may extend tens of kilometres. Furthermore, if the transmission loss is to be established or validated it would be necessary to measure as a function of range at a number of positions. Because of the variation in hammer energy during the pile-driving activity, particularly if a soft-start is employed, it is also desirable to perform the measurement independent of distance for the duration of the pile-driving operation. A number of others factors will also influence the noise radiated into the water column, including the water depth (exposing a different amount of the surface area of the pile), the seabed properties, the penetration depth into the seabed by the pile, the pile dimensions, and the hammer energy. Importantly, some of these factors may change during pile-driving of an individual pile, for example tidal variation and sediment penetration, and this means that the acoustic output is likely to change during the driving of a specific pile. A method for the measurement of this underwater noise, that is generally in relatively shallow water, which considers both the spatial and temporal variation of the sound field is described. The method includes a combination of fixed autonomous recorders and vessel based hydrophone deployments. The paper describes the activities within the International Organization for Standardization (ISO), Technical Committee 43, Sub-Committee 3, Working Group 3 to produce an international standards document to define the appropriate measurement methodology, which should be followed when measuring underwater noise radiated from marine pile-driving.
Assessment of the potential impact of underwater acoustic noise from both construction and operat... more Assessment of the potential impact of underwater acoustic noise from both construction and operation of almost all human marine activities is now commonplace within many international regulatory frameworks. More recent industries like offshore renewables (wind, wave and tidal) have experienced an increasing requirement to understand how their energy conversion devices interact with existing acoustic environments and what their potential for impacts might be. Assessing the potential for impact, however, results in a number of measurement challenges, for example, many of these devices represent highly complex, multi-modal, distributed sources which can be anything from arrays of many small (few meters) devices to larger systems with dimensions of hundreds of meters. The systems can also vary in nature from a floating device, for example a wave energy surface attenuator, or can be distributed throughout the water column, as can be the case for both wave and tidal systems, or wind turbine. In the case of an offshore wind turbine for example, the device is coupled to the seabed, and extends throughout the water column and in to the air. This distribution and configuration can make the measured acoustic characteristics strongly dependent on the environment, with the potential for propagation through the seabed, water and air, with complex interactions, particularly between the seabed and waterborne components of the sound. The environments themselves are also often acoustically complicated. For example, many of the devices are being developed in relatively shallow water where there is often strong bathymetric variation, and other natural and manmade noise sources. The devices themselves often also exhibit time variant characteristics. They can become more energetic with tidal speed, wave height wind speed increase, for example. Furthermore, these properties also alter the `natural' acoustic environment or baseline condition. The relationship between device noise and background or ambient noise is also likely to be fundamental to the effect these devices have on marine species, for example, by causing a change in behaviour or creating a masking effect. It may effect the detection capability of an animal, which may be important for collision avoidance. This paper discusses analysis of some of these challenges in the context of a number of emerging technology types. In particular, the paper considers the dynamically varying nature of the ratio of the noise radiated from the device to the background noise. Data is presented of the operational noise levels against the background noise levels, under different sea-states for a full-scale attenuator wave energy system.
The underwater and airborne acoustic environment forms a critical part of many marine mammals lif... more The underwater and airborne acoustic environment forms a critical part of many marine mammals life cycles. Assessment and development of understanding of these acoustic soundscapes is often vital in understanding many marine life and human operation interactions as well as species to species interactions in the natural acoustic environments. Traditional passive acoustic methodologies used for underwater sound and noise measurements include static hydrophones, autonomous loggers, boat-based deployments, towed arrays, drifter systems etc. Most of these systems however also rely on expensive and sometimes hazardous deployments and retrieval methods. The rapid growth in Unmanned Ariel Vehicles (UAV) technologies in recent years has lead to investigation of these platforms to act as enhanced aerial visual platforms for observing marine mammal behaviour, abundance estimation etc. These systems are however often limited by battery life to relatively short in flight deployments. However these platforms can also offer the opportunity for rapid deployment of smart hydrophone systems over a relatively large spatial areas to include acoustic behaviours and sound scape analysis by flying to a site landing on the water and then deploying underwater sensors. Whilst on the waters surface relative power consumption is significantly lower than in-flight allowing significantly longer deployments. Smart systems will then return to some base point with minimal human interaction. A prototype multi-rotor system has been developed and tested in an open water site, capable of flying to site, landing on the water, deploying a wideband hydrophone for underwater noise assessment and then returning to base. Measurements include underwater noise self-noise analysis in-flight, landing, static and take-off and potential implications to marine wildlife. These developments and trials have demonstrated the overall feasibility of wide-scale rapid hydrophone deployment using UAVs for sound field and marine mammal behaviour analysis.
Journal of the Acoustical Society of America, May 1, 2017
Traditional operations such as oil and gas exploration and production have long undergone sound f... more Traditional operations such as oil and gas exploration and production have long undergone sound field and environmental impact assessments of underwater acoustic noise. More recently emerging industries such as renewables (wind, wave, and tidal energy production) have also required scrutiny in terms of underwater noise sound fields. To make these assessments, sound fields are typically measured using hydrophones deployed from boats, drifting systems or moored acoustic data loggers. These measurements are often complex and expensive requiring complicated equipment deployments, boat operations and personnel in often-dangerous or hazardous environments. Unmanned Ariel Vehicles (UAV) or drone based technologies offer the opportunity for rapid deployment of smart hydrophone systems arrays over a large spatial area with significantly lower operator and boat interaction improving deployment flexibility, cost and minimising safety concerns for boat based deployments. Results presented are from tests of a prototype multi-rotor system in an open water site, capable of flying to site, landing on the water, deploying a wideband hydrophone for underwater noise assessment and then returning to base. These developments and trials have demonstrated the overall feasibility of wide-scale rapid hydrophone deployment using UAV based sensors and its potential application to underwater sound field assessment across a variety of industries.
Journal of the Acoustical Society of America, May 1, 2017
Tidal-stream turbines are a promising source of renewable electricity worldwide. These technologi... more Tidal-stream turbines are a promising source of renewable electricity worldwide. These technologies are sufficiently new that only single test devices have been deployed with arrays imminent. Being new, their interactions with marine organisms are poorly understood and the risk of large marine vertebrates colliding with their moving blades is a consenting and ecological concern. Operational noise is also considered a disturbance threat but under what circumstances is poorly defined. Further, the threats of collision and turbine noise may be inversely correlated with animals needing to hear turbines to avoid them. Consequently, there have been proposals to add extra-noise by fitting turbines with acoustic deterrents to warn or scare animals away. In this talk we examine the acoustic interactions between marine mammals and tidal turbines. The interactions are complex and depend on turbine source levels, ambient sound, propagation in moving water, sensory abilities, swim speeds and diving behaviour. In addition, the occurrence of turbines in arrays adds further complexity as responses to one turbine will impact collision risk with another. We then consider the options for and implications of adding additional warning sounds but such quick fixes might have unintended consequences that either increase collision risk or lead to undesirable avoidance.
Journal of the Acoustical Society of America, Oct 1, 2019
The growth of interest in the development of harnessing tidal energy has also led to the requirem... more The growth of interest in the development of harnessing tidal energy has also led to the requirement of assessment of underwaters sound fields in these environments. The radiated acoustic signatures of underwater systems in these environments is of significant interest. The measurements of the sound field in tidal flow areas however offer a number of major challenges. In a high flow environment, a static hydrophone would often suffer from significant flow noise. This parasitic noise is not real in the environment but a result of water column particle interaction with the hydrophone surface and has the capability of severely limiting the systems dynamic range for assessment of the true acoustic environment. Drifting system, moving at the speed of the water flow minimise this by reducing fluid particle to sensor interactions however are constrained by both temporal and spatial variations during the drifting limiting the ability to continuously monitor a system. Flow shield technology (sonar domes) have however been used extensively of the reverse problem of high-quality sound reception from a moving platform essentially suffering from the same problem. Work is presented on the use flow shield concept for a proto-type seabed mounted static recorder deployed in a high flow environment.
Acoustics can provide important information to assess underwater resources, noise and wildlife in... more Acoustics can provide important information to assess underwater resources, noise and wildlife interactions on marine energy sites. The European Marine Energy Centre (EMEC) has collaborated on a number of projects to develop acoustic technology, methods and quality control of monitoring techniques used for such assessments. This paper outlines previous and current activities at EMEC in this area, with a focus upon beneficial advances through knowledge exchange with Loughborough University and other knowledge partners.
This good practice guide was prepared by Stephen Robinson of the National Physical Laboratory wit... more This good practice guide was prepared by Stephen Robinson of the National Physical Laboratory with the assistance of Dr Paul Lepper (Loughborough University) and Dr Richard Hazelwood (R&V Hazelwood Associates). The work to develop new guidance has built upon the expertise already gained by researchers in a number of countries who have been actively engaged in discussions on this topic for some time. It is these informal discussions that have led to the initiation of standardisation work within ISO.
1. ABSTRACT The use of envelope detection methods to reduce the bandwidth of an echolocation clic... more 1. ABSTRACT The use of envelope detection methods to reduce the bandwidth of an echolocation click into the audio-band is not a new concept. However, the increasing popularity of portable digital recorders with excellent signal to noise performance needs such signal processing if ultrasonic transient data needs to be captured. Similarly, this approach allows high frequency information to be recorded onto video recorder sound tracks providing the advantage of synchronised sound with images for behavioural studies. This paper describes the development of a new generation of ECD with improved performance and includes cetacean echolocation data recorded using this equipment in two independent studies.
Conventional underwater based acoustic deployment platforms, such as boats, drifting systems or m... more Conventional underwater based acoustic deployment platforms, such as boats, drifting systems or moored long term acoustic data loggers are often expensive, complex and are usually deployed in dangerous environments. A novel alternative involving the use of a waterproof Unmanned Aerial System (UAS) for the deployment of underwater acoustic sensors is presented. The system has the capability of overcoming the limitations of current deployment methods, while also being able to self-deploy and self-retrieve, and will improve deployment and redeployment times.
A framework to predict, validate and review the acoustic footprints of operating tidal turbines [... more A framework to predict, validate and review the acoustic footprints of operating tidal turbines [abstract]
Environmental dependence of underwater sound propagation resulting from percussive pile driving [... more Environmental dependence of underwater sound propagation resulting from percussive pile driving [abstract]
Pile-driving of marine foundations can radiate substantial levels of low-frequency impulsive nois... more Pile-driving of marine foundations can radiate substantial levels of low-frequency impulsive noise into the water column, which given the right acoustic propagation environment conditions can propagate over large distances. Concern over the potential for impact on marine fauna often results in a regulatory requirement to measure the radiated noise level over distances which may extend tens of kilometres. Furthermore, if the transmission loss is to be established or validated it would be necessary to measure as a function of range at a number of positions. Because of the variation in hammer energy during the pile-driving activity, particularly if a soft-start is employed, it is also desirable to perform the measurement independent of distance for the duration of the pile-driving operation. A number of others factors will also influence the noise radiated into the water column, including the water depth (exposing a different amount of the surface area of the pile), the seabed properties, the penetration depth into the seabed by the pile, the pile dimensions, and the hammer energy. Importantly, some of these factors may change during pile-driving of an individual pile, for example tidal variation and sediment penetration, and this means that the acoustic output is likely to change during the driving of a specific pile. A method for the measurement of this underwater noise, that is generally in relatively shallow water, which considers both the spatial and temporal variation of the sound field is described. The method includes a combination of fixed autonomous recorders and vessel based hydrophone deployments. The paper describes the activities within the International Organization for Standardization (ISO), Technical Committee 43, Sub-Committee 3, Working Group 3 to produce an international standards document to define the appropriate measurement methodology, which should be followed when measuring underwater noise radiated from marine pile-driving.
Assessment of the potential impact of underwater acoustic noise from both construction and operat... more Assessment of the potential impact of underwater acoustic noise from both construction and operation of almost all human marine activities is now commonplace within many international regulatory frameworks. More recent industries like offshore renewables (wind, wave and tidal) have experienced an increasing requirement to understand how their energy conversion devices interact with existing acoustic environments and what their potential for impacts might be. Assessing the potential for impact, however, results in a number of measurement challenges, for example, many of these devices represent highly complex, multi-modal, distributed sources which can be anything from arrays of many small (few meters) devices to larger systems with dimensions of hundreds of meters. The systems can also vary in nature from a floating device, for example a wave energy surface attenuator, or can be distributed throughout the water column, as can be the case for both wave and tidal systems, or wind turbine. In the case of an offshore wind turbine for example, the device is coupled to the seabed, and extends throughout the water column and in to the air. This distribution and configuration can make the measured acoustic characteristics strongly dependent on the environment, with the potential for propagation through the seabed, water and air, with complex interactions, particularly between the seabed and waterborne components of the sound. The environments themselves are also often acoustically complicated. For example, many of the devices are being developed in relatively shallow water where there is often strong bathymetric variation, and other natural and manmade noise sources. The devices themselves often also exhibit time variant characteristics. They can become more energetic with tidal speed, wave height wind speed increase, for example. Furthermore, these properties also alter the `natural' acoustic environment or baseline condition. The relationship between device noise and background or ambient noise is also likely to be fundamental to the effect these devices have on marine species, for example, by causing a change in behaviour or creating a masking effect. It may effect the detection capability of an animal, which may be important for collision avoidance. This paper discusses analysis of some of these challenges in the context of a number of emerging technology types. In particular, the paper considers the dynamically varying nature of the ratio of the noise radiated from the device to the background noise. Data is presented of the operational noise levels against the background noise levels, under different sea-states for a full-scale attenuator wave energy system.