Measurement and characterisation of radiated underwater sound from a 3.6 MW monopile wind turbine

This paper describes underwater sound pressure measurements obtained in close proximity (50 m) to two individual wind turbines, over a 21-day period, capturing the full range of turbine operating conditions. The sound radiated into the water was characterised by a number of tonal components, which are thought to primarily originate from the gearbox for the bandwidth measured. The main signal associated with the turbine operation had a mean-square sound pressure spectral density level which peaked at 126 dB re 1 lPa2 Hz 1 at 162 Hz. Other tonal components were also present, notably at frequencies between about 20 and 330 Hz, albeit at lower amplitudes. The measured sound characteristics, both in terms of frequency and amplitude, were shown to vary with wind speed. The sound pressure level increased with wind speed up to an average value of 128 dB re 1 lPa at a wind speed of about 10 ms 1, and then showed a general decrease. Overall, differences in the mean-square sound pressure spectral density level of over 20 dB were observed across the operational envelope of the turbine

Theoretical determination of the long term contributions to ambient noise levels from offshore wind farm construction

Marine pile driving during offshore wind farm construction may increase the anthropogenic component of ocean ambient noise and has led to increasing concerns regarding its effects on the marine fauna (receptors)1. In the case of many static offshore developments two commonly used foundation techniques are tripod and jacket constructions involving installation of a series of smaller diameter piles surrounding a central structure and mono-piles using a single larger diameter pile. Pile installation itself may involve sequences of percussive piling at different hammer energies, vibro-piling (more rapid, lower level vibrations) and drilling. In some cases all three techniques are used on a single pile installation, with the construction phase lasting several hours for each pile, and with perhaps 50 - 100 turbine supports in a typical windfarm development

The contribution to anthropogenic noise from marine aggregate extraction operation in UK waters

As of 2009, there were 75 licensed areas within UK waters for marine aggregate extraction. Each year, around 20 million tonnes of sand and gravel are extracted from these areas for use in the construction and building industry1. Extraction of marine aggregate has the potential to generate noise, and if at sufficient levels, this could have a negative impact on marine species in or around the dredging area. However, measurement of the noise generated during marine aggregate extraction has been limited, particularly in UK waters. The most extensive measurements were undertaken in the Beaufort Sea during oil exploration in the 1980s2,3. Other measurements around Sakhalin Island have been reported in the literature, which were compared by Ainslie et al4 to other vessels including the Overseas Harriette5. This paper presents the results of underwater noise measurements for six different dredgers measured in three locations around the UK, with aggregate type varying from sand to coarse gravel. From the measurements of radiated noise for dredgers under normal operation an estimate is made of the long term contributions to ambient noise levels from typical dredgers under normal operation, the contribution to the overall ambient noise budget, and the cumulative Sound Exposure Level for receptors in the vicinity

Measurement of underwater noise arising from marine aggregate dredging operations

This is the final report for project MALSF MEPF 09/P108, funded by the Aggregate Levy Sustainability Fund, the aim of which is to provide data for the typical underwater radiated noise levels from marine aggregate dredgers in the UK fleet during normal operations. The work is aligned with the stated aims of the ALSFMEPF to reduce the environmental footprint of marine extraction of aggregates, and follows directly from the key knowledge gap identified in the initial scoping study conducted in MEPF Project 08/P21 [Thomsen et al, 2009]. The key finding of the study is the noise output of dredging vessels is similar to a ‘noisy merchant vessel’ and is substantially quieter in terms of acoustic energy output than some other anthropogenic noise sources such as seismic airguns and marine pile driving. This project has been an extensive study of the noise generated by the UK’s fleet of trailing suction hopper dredgers during marine aggregate extraction. The objectives of the work were (i) to develop a suitable methodology for measuring underwater noise radiated by dredgers, (ii) undertake measurements on UK dredgers at up to four sites and report, whilst disseminating the results to the wider stakeholder community. In the report, data is presented for 6 vessels, measured across 3 different areas around the UK’s coast

The measurement of underwater noise radiated by dredging vessels during aggregate extraction operations

The total marine aggregate extracted from the seabed in UK waters can exceed 20 million tonnes each year, and there is a need to understand the noise generated during the extraction process in order to evaluate any potential impact on the marine environment. For aggregate extraction, the type of vessel used is a trailing suction hopper dredger, which lowers a drag head and suction pipe to the sea floor to extract the sand or gravel, depositing it in a hopper on the vessel, whilst returning unwanted material and water over the side of the vessel. There are a number of potential noise generation mechanisms during this type of dredging activity. This paper presents the results of underwater noise measurements for six different dredgers measured in three locations around the UK, with aggregate type varying from sand to coarse gravel. One vessel was measured in two different areas with different aggregate types. The methodology used to derive the source level for the dredgers is described, and the results of an investigation undertaken into the origin of the radiated noise is given. Measurements were made at frequencies up to 100 kHz, with limited data obtained up to 200 kHz. Noise levels are shown for the same dredger under different operational modes, illustrating that the noise output level is partially dependent upon the mode of operation and the aggregate type being extracted

Study on association of working hours and occupational physical activity with the occurrence of coronary heart disease in a Chinese population

<div><p>Objective</p><p>To explore the association of working hours and occupational physical activity (OPA) with the occurrence of coronary heart disease (CHD) in a Chinese population.</p><p>Methods</p><p>A total of 595 participants (354 and 241 patients with and without CHD, respectively) aged between 24 and 65 were enrolled in our study, which was conducted at the First Affiliated Hospital of Nanjing Medical University between December 2015 and October 2016. Participant characteristics were collected from face-to-face questionnaires, and logistic regression analysis was conducted to examine the association of working hours and OPA with the occurrence of CHD.</p><p>Results</p><p>Compared with non-employed people, long working hours (especially ≥55 hours/week) contributed to the occurrence of CHD (adjusted odds ratio[OR] = 2.213, 95% confidence interval [CI]: 1.125, 4.355, P = 0.021) after multivariate adjustment in the Chinese population. With the extension of worktime, the CHD risk increased (P for the dose-response trend = 0.022). Meanwhile, even after adjusting for engagement in physical activity during leisure time, sedentary behavior at work had an adverse effect on CHD risk (adjusted OR = 2.794, 95%CI: 1.526, 5.115, P = 0.001), and a linear relationship was also found between OPA and CHD (P for the trend = 0.005).</p><p>Conclusions</p><p>Long working hours and sedentary behavior at work are associated with a high risk of CHD. In addition, prolonged working hours in sedentary occupations increases the risk of CHD, independent of engagement in leisure time physical activity.</p></div

Characteristics of CHD and non-CHD groups.

<p>Characteristics of CHD and non-CHD groups.</p

Relationship between worktime, OPA and the risk of CHD.

<p>Relationship between worktime, OPA and the risk of CHD.</p

Multivariate logistic regression for CHD risk factors.

<p>Multivariate logistic regression for CHD risk factors.</p

Distribution of worktime between sedentary and non-sedentary employed population.

<p>Distribution of worktime between sedentary and non-sedentary employed population.</p