But she added: ‘The most common sound is the so-called rumbling, that sounds rather like the engine of a truck.
‘The lowest frequency component is in the infrasound range and is not audible to us humans, but with our special equipment we can also record the deep sounds.’
The subject of the thesis is ‘Early mother-child communication among African elephants in the zoo’ and Mr Gorofsky has been given unlimited access to all areas of the elephant park the same as keepers in order to record what he needs.

Sounds good: Christopher Gorofsky is carrying out some of the research as part of his Masters

Monitoring: The mum and baby elephant;Scientists using sensitive microphones have been recording the way this baby female elephant is learning to speak to her mum
He said: ‘In the beginning Kibali made hardly any sounds. Communication however since then been steadily increasing. If she wants to drink with her mother, she makes a kind of squeak.’
But he also noted that communication included body language which was used by Kibali to indicate whether she wanted to drink or play, or indicate she has heard when her mother calls for her.
The baby elephant was named after a river in the Democratic Republic of Congo, and mother Numbi, 20, already has raised two baby elephants after coming to Vienna in 2009.

The pair were chosen because Numbi was clearly experienced enough to make her developing relationship with the new baby of interest to the research team.