Contact call

Contact calls are seemingly haphazard sounds made by many social animals (such as a chicken's cluck). Contact calls are very different from many other types of calls (for example, alarm calls), as contact calls are not a specific signal, designed to communicate some specific information. It is rather a mixture of various sounds, accompanying the group's everyday business (for example, foraging). Contact calls are used to maintain audio contact with the members of the group. Some social animal species communicate the signal of potential danger by stopping contact calls, without the use of alarm calls. Charles Darwin wrote about this in relation with wild horse and cattle.

Humming as contact calls

Joseph Jordania suggested that human humming could have played a function of contact calls in early human ancestors. According to his suggestion, humans find it distressing to be in full silence (which is a sign of danger for them), and this is why humans who are alone sometimes hum, whistle, talk to themselves, or listen to TV or radio during other activities.