Along with Quality, Health and Safety, Environment is one of the core pillars here at OSC Marine. Recently, one of our clients asked us to take underwater acoustic measurements at a number of points to assess whether the marine life in the area is being disturbed or is at risk.
Why do we take underwater acoustic measurements?
Along with assessing how underwater industrial noise affects marine life, underwater acoustic measurements are also used for underwater communications, offshore engineering and studying our oceans. Due to the environmental impact industrial noise can make in our seas and the importance of learning more about these habitats, the need for underwater acoustic measurement services has been increasing.
The case study
Recently, an OSC Marine Group client sent us their 17 monitoring points, each strategically plotted around a vesselpowership.
All of our underwater noise measurements were focused on reading sound pressure levels (SPLs) from industrial works and the marine life itself in the water columns surrounding the monitoring points. We began to measure SPLs from the vessel engines and machinery, as well as echosounders (a device that uses sonar to measure underwater components, biological or physical) and hydrostatically-induced signals taken from surface wave motion.
Performing this kind of survey based from a vessel is common practice for a variety of acoustic monitoring operations. With the analysis and recording equipment remaining safely on the small boat, hydrophones are deployed in arrays or individually. A hydrophone is an instrument that works just like a microphone, measuring the intensity of underwater sounds. They can pick up the sounds of whales, dolphins and even shrimp! But hydrophones aren’t without their industrial applications as well. They monitor pile driver noise and sound pressure levels created by air gun arrays, for example.
Benefits of vessel deployment
We launched small boats to the 17 GPS locations indicated by our client. While this may seem counterintuitive at the offset, vessel-based surveys serve their purpose well, offering one of the best solutions for measurement configuration. Deployments are quick and mobile and can cover large areas fairly cost-effectively, which many clients appreciate. Since most of the equipment is kept on the vessel (with the hydrophone doing the work down below). Other benefits are that the data can be monitored in real time and instrument settings can be adjusted accordingly in the moment, all ensuring the highest possible quality data.
Is there a place for a simpler methodology?
The methods we use to sample data will always be influenced by the purpose of the measurements and our clients’ needs. If the objective is to determine background noise levels that influence a measurement of radiated noise for a specific source, a simpler methodology can be used. For example, we would take a snapshot of the sound/s in questions from a short-term deployment over a short period of time, usually only between a few minutes to an hour. We will also often take a measurement before or after radiated noise as a control.
Contact OSC Marine
June is National Environment Month here in South Africa, and this always serves as a reminder to consider the effects we are having on our environment. Just as the client in the case studied details above wanted to assess the impact their works were having on marine life, you too can get in touch with OSC Marine for any of your underwater acoustic measurement needs.