Background Noise Levels
Background noise is likely to be derived from a variety of sources which include:
- Traffic noise (e.g. A2, A13, A1014 and A1089 which run near by to the designated sites);
- Industry and dockyards (e.g. Port of Tilbury, Shell Bravo, etc);
- Temporary construction noise (i.e. proposal for new container and roro facilities at the Shellhaven site); and
- Water-borne noise from vessels and people.
One of the main sources of noise for the birds of the SPA will be a result of the passage of boat traffic. The Port of London is one of the busiest ports in England, with more than 80 terminals, and is a gateway to London and the south-east of England. The PLA has various by-laws in place regarding the control of noise levels within this area. This includes by-law 47(1):
"No person shall use or knowingly cause or permit to be used a vessel with an internal combustion engine unless the engine is fitted with a silencer, expansion chamber or other contrivance suitable and sufficient for reducing so far as may be reasonable the noise caused by the escape of exhaust gasses from the engine; provided that the engine may be fitted with a device for cutting out the silencer expansion chamber or other contrivance so long as the device is used only to enable the engine to be started and for no other purpose".
Such by-laws limit the disturbing effect of noise for both the users and residents of this waterway, but will also reduce the possible impacts on the wildlife communities as well.
The main source of noise from a vessel originates from the engine, and may travel via the atmosphere or be transmitted through the structure of the craft. The volume of sound generated and transmitted into the air or water depends on the size, design and location of the engine, and the craft's size and construction. Vessel-based ornithological surveys have previously found that the birds are initially disturbed by the presence of a boat. However, dredgers are generally quieter than such survey vessels (PLA, Princes Channel Environmental Assessment Report, 2004).