Skip to content

What Do Human Ears Miss?

Updated Friday 16th July 2004

Learn more about ultrasound and infrasonic communication

Elephants - more to them than meets the ear Copyrighted image Icon Copyright: Production team For many animals communication through a repertoire (range) of calls is an important part of their everyday lives and may be a factor in whether or not they pass on their genes. Some groups of animals, however, even have a mastery of sound utterly outside the usual human experience.

The pipistrelle bat is still one of the most widespread of bats in Britain, despite suffering major declines in the last 35 years (perhaps 70%). It is also one of the most often-encountered bats, despite its small size, as it inhabits suburban parks and gardens as well as woodland edges and watersides. Pipistrelles navigate their way through the night using echolocation, a series of short, high-frequency sounds (bats emit sounds between 9 and 200 kilohertz, most of which is well above the range of human hearing), often very loudly (about the volume of a smoke alarm, if we could hear them). These high-pitched (ultrasound) squeaks bounce off objects in the bats’ path and return, providing information an object’s size, shape, type, distance and direction, as well as whether or not it is moving. Tiny insects such as gnats can be detected, making nocturnal insectivorous bats effective aerial hunters! Such bats effectively “see” in sound, forming a picture of their dark world which enables them to avoid obstacles and capture their otherwise invisible prey.

In contrast to the “bouncy” ultrasound, low-frequency sound (infrasound – which is below the range of human hearing) is employed by animals precisely because it tends to roll around objects in its path. It is therefore a useful means of long-distance communication. Up until the mid-1980s, researchers marvelled at the ability of separated groups of African elephants to find one another on the savannah, as well as that of solitary males to locate groups of females for mating. It was then discovered that they stay in contact using “rumbles” largely in the infrasonic range (frequencies of between 1 and 20 hertz); although a component of elephant calls may be detectable to human ears. Low frequency sounds have a longer sound wave, and can therefore travel further without being absorbed or bounced back. Playback experiments using savannah and forest elephants suggest that they can stay in touch over distances of at least four kilometres, and that infrasound communication works just as well in dense forest.

 

For further information, take a look at our frequently asked questions which may give you the support you need.

Have a question?

Other content you may like

Cybertalk: Transcript Copyrighted image Icon Copyright: Thinkstock article icon

Science, Maths & Technology 

Cybertalk: Transcript

New technology is changing the way we communicate. Digital Planet found out how.

Article
Connecting: Connecting with drama Copyrighted image Icon Copyright: BBC article icon

TV, Radio & Events 

Connecting: Connecting with drama

We explore how Radio 4's Connecting series dramatises the opportunities and risks of modern communication technologies

Article
Tracking a group of bonobos Creative commons image Icon Work found at http://en.wikipedia.org/wiki/Bonobo / CC BY-SA 3.0 under Creative-Commons license audio icon

Nature & Environment 

Tracking a group of bonobos

Theo Webb and Gottfried Hohmann track a group of bonobos in the Democratic Republic of Congo.

Audio
15 mins
Studying mammals: Food for thought Copyrighted image Icon Copyright: Used with permission free course icon Level 1 icon

Nature & Environment 

Studying mammals: Food for thought

Who were our ancestors? How are apes and humans related? And where does the extinct Homo erectus fit into the puzzle? In this free course, Studying mammals: Food for thought, we will examine culture, tool use and social structure in both apes and humans to gain an understanding of where we come from and why we behave as we do. This is the tenth course in the Studying mammals series.

Free course
10 hrs
Endangered green turtles Creative commons image Icon The Open University under Creative Commons BY-NC-SA 4.0 license video icon

Nature & Environment 

Endangered green turtles

Many green turtles come to nest on Raine Island but, for some, says Dr Andrew Dunstan, it is literally an uphill struggle.

Video
At the water's edge: Blakiston's fish-owl Copyrighted image Icon Copyright: Thinkstock audio icon

Nature & Environment 

At the water's edge: Blakiston's fish-owl

From a nature reserve in Japan, the Saving Species team is joined by experienced field ornithologist, Mark Brazil, in an extended interview as they observe some Blakiston's fish-owls and also spot some unexpected Steller's eagles.

Audio
15 mins
Do whales commit suicide? Creative commons image Icon Bahnfrend under CC-BY-SA licence under Creative-Commons license article icon

Nature & Environment 

Do whales commit suicide?

Are humans the only animals who kill themselves, or do other species commit suicide as well? David Lusseau considers the case of whale beachings.

Article
Life on the Beach Creative commons image Icon markkilner under CC-BY-NC-SA licence under Creative-Commons license article icon

Nature & Environment 

Life on the Beach

Patricia Ash introduces the range of life you can find on British beaches

Article
Darwin Now: Out of Africa Copyrighted image Icon Copyright: The British Council video icon

Nature & Environment 

Darwin Now: Out of Africa

Sheila Ochugboju describes how Darwin has inspired her own personal and professional journey. How is she bringing his legacy to life for young people in her native Africa?

Video
5 mins