How Do We Listen In?

Used with permission Infrasound monitoring has become an important tool for scientists assessing populations of endangered forest elephants in Africa. Specialist equipment (sensitive to sounds at low frequencies) is required to record the calls and store them as digital information. They can then be analysed both audibly, by speeding up the call (raising its frequency), and visually (as a graphical representation of the sound waves). Elephant conversations in dense forest can be automatically recorded in this way over periods of several months.

The development of these infrasound recording techniques has allowed the study of elephants which are otherwise difficult to even find! Scientists also use acoustic monitoring to assess populations of other endangered animals such as grasshoppers, bats, badgers and amphibians, as well as introduced insect pests.

In North America in particular (although the method is applicable to other parts of the world), conservationists use volunteers trained to recognise the calls of different frogs and toads to monitor the presence of breeding males at ponds. Repeat calling surveys over a period of years can then be used to assess changes in species abundance and distribution.

This research could be especially important as amphibians are known to be particularly sensitive to environmental changes – changes which, in time, can have detrimental effects to human health and quality of life. An understanding of the acoustic environment might therefore be just as important to Brian from Personnel as it is to a hunting bat.