A unique challenge was presented to Bowers & Wilkins recently when we were asked to custom build two loudspeakers capable of reproducing the very low frequencies associated with the ‘contact rumbles’ of female African elephants.
This unusual request came to Gary Geaves from Dr Karen McComb who is based in the Psychology Department, University of Sussex. Karen leads a research group, which focus on communication and cognition in a range of mammalian species from red deer to African elephants.
- In this latest project Karen and Postdoctoral Research Fellow Dr Graeme Shannon are planning to explore the role of age and experience in the acquisition of social and ecological knowledge in elephants. In a previous study it was demonstrated that the social knowledge of one key individual in the family unit – the oldest female or matriarch – can determine the social knowledge of the whole group. More specifically, families with older matriarchs were significantly more effective than families with younger matriarchs at distinguishing the contact calls of genuine strangers from those of more familiar associates – and this translated into reproductive benefits for their groups.
- In order to now investigate more comprehensively how the age and specific experience of the oldest individual within a group contributes to the knowledge and successful operation of the group as a whole, the researchers required a pair of identical loudspeakers capable of broadcasting the low frequencies of elephant rumbles with very high fidelity. These will be used to play elephant calls to family groups in Amboseli National Park, Kenya and Pilanesberg National Park, South Africa, allowing a comparison between the leadership abilities of matriarchs in natural family groups (in Kenya) versus those that are in groups that have been artificially formed through translocation (South Africa). The loudspeakers will be mounted in the back of a Land Rover and once an elephant group is located and identified the playback experiment is carried out using pre-recorded and re-synthesised elephant calls. The call is broadcast when the elephants are 100 m from the Land Rover and their behavioural responses (listening, defensive bunching etc) are filmed using a high definition video camera.
A motivation to support local researchers at the University of Sussex, coupled with the technical expertise and excitement of a novel challenge, led B&W to provide full backing for this project. The construction of the two identical loudspeakers began in March 2009, with Stephen Entwistle taking the lead in design. As well as being able to produce frequencies as low as 10 Hz (significantly lower than those which can be detected by the human ear), the loudspeaker must also be powerful enough to reproduce the elephant calls at a sound level 105 decibels – approximately the amplitude produced by a large female elephant. These requirements have resulted in a speaker that weighs 90 kg and has a volume of approximately 360 litres! The unique design also needed to incorporate powerful amplifiers inside the wooden cabinet of the speaker.
Check back soon for more on Bowers & Wilkins and the elephant subwoofer…