During a seismic survey, strong impulses of waterborne sound are emitted by arrays of airguns which release air at high pressure into the water. The sound returning from the seabed is processed to allow an image of the rock strata and underlying geological structures underneath the seabed to be formed. In addition to the sound that travels downwards into the seabed, the sound from the airguns also travels sideways through the water, and this noise has been cited as causing environmental effects.
Over the past 23 years, Subacoustech has been involved in measuring the noise from seismic surveys in partnership with marine biologists specialising in fish and marine mammal biology.
The North Sea, Wytch Farm and Meldorfer Bucht surveys illustrate the noise propagation from seismic surveys. They have been selected from our data sets to illustrate deep water, coastal water and very shallow water surveys respectively. Click below to see a summary report for each site:
To understand the environmental effects of a seismic survey, a measurement scheme for the data needs to be defined, then the measurements must be analysed according to that scheme, and fitted into a model that enables general conclusions to be made.
Subacoustech’s work on audiograms and hearing thresholds (dBht) allows data taken in seismic surveys to be interpreted in a way that represents how the noise is perceived by different species according to their hearing abilities. For example, according to their audiograms, the hearing ranges of fish are within much lower frequencies than marine mammals. More information can be found in Audiograms and the dBht