Estimation of Impact Zones

In general, measurements or estimates of noise are relatively easily made. A critical part of the process however is being able to analyse the noise in a way that will assess the environmental effect of noise, so that the measurements can be interpreted and processed in a biologically significant way.

Estimated zones for the levels of noise which can cause potential lethal, physical, and auditory damage are known, and are evaluated in the model.

Levels of noise which may cause behavioural avoidance of a particular species will depend on the hearing ability of the species. If the animal cannot 'hear' the sound i.e. it is outside of the threshold of its hearing ability, it won't avoid it.

The dB_ht(Species) metric (currently undergoing validation as part of a DTI funded research programme) has been developed by Subacoustech for this task. It gives a species specific noise level referenced to an animal's hearing ability, and therefore a measure of the potential of the noise to cause an effect.

This is very important because even apparently loud underwater noise may have no effect on an animal if it is in a frequency range that the animal cannot hear (e.g. humans inability to hear a dog whistle).

To read more about the science behind dB_ht and the audiograms from which the hearing threshold (ht) for the species is evaluated, click here.

The modelling process can estimate the species-specific Transmission Loss values, so that the ranges at which the noise would be significant enough to potentially cause avoidance behaviour for relevant species, can be predicted, and the estimation of an avoidance limit can be evaluated. The model uses conservative values to give the greatest estimated ranges at all times.

To discuss your particular environment and species specific to your location please contact us.