The Environment Protection Authority (EPA) has released the results of an investigation into the noise emitted by the Ronja Huon, a vessel used to service marine farms in the Huon River and D’Entrecasteaux Channel, and concluded that the noise is within the regulated limit.
The EPA investigated the noise emissions in response to a number of disturbance complaints about the vessel since it began operating in 2015. The complaints were received by several agencies and related to a range of noise sources, including the operation of the vessel’s generators in Port Huon, the vessel’s transit in front of residences on the riverbanks of the Huon River, and its operation at leases near the mouth of the Huon River (as heard from areas such as Roaring Beach, Surveyors Bay and Lunawanna, Bruny Island). These complaints represent a considerable range of source to receiver distances, from some hundreds of metres for Port Huon residents hearing the vessel at the Port Huon pier to well over 10 km for on-lease noise reaching Lunawanna.
The Ronja Huon which is a modern ‘Well Boat’ built in Norway, is under contract to Huon Aquaculture for its marine farming activities in the lower Huon River, Channel and eastern side of Bruny Island. The vessel, which is 76 metres long, is used for bathing and transporting of fish, and was leased by Huon Aquaculture for its speed and operational efficiency. It also promised to reduce noise by replacing the tow boats which were previously required to tow pens of fresh water for fish treatment. When it began operating in early 2015, however, the vessel was not setup for receiving shore-power and on-board generators were required to be kept running when the vessel was portside. This situation has now been rectified and shore-power for the vessel is available at Port Huon.
The EPA’s investigation was focused on the technical characteristics of the noise emitted from the vessel, using measurements and audio recordings made at five main locations. These recording sites related directly to the complaints of disturbance from vessel noise. They provide useful measurements of vessel noise from different distances and take account of the ambient noise conditions which may vary significantly.
The measurements were made with Acoustic Research Laboratories Ngara noise loggers, measuring both A and C frequency weighted noise levels at a rate of 10 measurements per second. While the A-weighted values are aligned to the frequency response of the human ear, the C-weighted values include lower frequency sounds, which is an advantage for identifying noise from the Ronja Huon.<
A range of aspects of the noise from the vessel were identified through the measurements. The main component of the noise was found to be a significant tonal peak at 45 Hz, which tends to dominate the noise and is almost totally responsible for the resulting A-weighted noise level at any distance from the vessel. The noise from the vessel also contains many smaller tonal peaks that are within a series of harmonics based on a fundamental of 7.5 Hz.
A copy of the full noise report, Impact of Vessel Noise at Wattle Grove, is available on the EPA website. It provides details and interpretation of the acoustic measurements made of the vessel noise in the Huon River and to a lesser extent, the D’Entrecasteaux Channel. The report focuses on the technical characteristics of the vessel’s noise emission rather than providing an interpretation of the degree of impact. A key finding was that the results were consistent with environmental regulations, namely that the vessel does not emit a noise greater than 74 dB(A) over a distance of 25 metres. This is the limit specified in Regulation 8(1) of the Environmental and Pollution Control (Miscellaneous Noise) Regulations 2014.