Echolocation

This article covers the general procedure. For occurrence in animals and humans, see echolocation (disambiguation) .

Echolocation is the detection of the location and type of objects by emitting sound or radio waves and analyzing the waves reflected by the objects . The method is used both in animals and in technology - and in blind people (with tongue click, the so-called click sonar ).

Principle of echolocation

In echolocation, sound or radio waves are actively emitted. If the waves hit an obstacle, they are thrown back. The distance to the obstacle can then be determined from the travel time of the waves. The exact direction in which the obstacle is located can also be determined, as well as the size of the obstacle.

The direction from which the echoes arrive can be determined with the help of several receivers at different points. The direction of the echo and thus the direction of the obstacle can then be determined from the differences in transit time between the receivers.

An alternative to using multiple receivers is to use pivotable transmitters and receivers and send bundled signals. Then only obstacles are detected that are currently in the direction of the "transmitting lobe". The sending and receiving direction then corresponds to the direction of the obstacle.

In order not to have to wait until all reflections have arrived after sending a wave packet, the transmitter can also send continuously, but with a time-dependent frequency. The time at which this frequency was sent results from the frequency with which an echo arrives at the receiver and from this the transit time and thus the distance of the obstacle. The same effect can be achieved by sending time-dependent codes. By comparing the point in time at which the code just received was sent, the recipient can determine the transit time and, from this, the distance.

Application of echolocation in technology

Humans have made use of echolocation through several techniques.

• When radar " ra dio d etection a nd r was concerned" (about finding and distance measurement with radio waves) high-frequency radio waves are emitted. The radio waves are only optimally reflected back by metallic objects. The main application is in aviation and shipping.
• Sonar is an English acronym for " so und, n navigation a nd r anging", which means something like sound navigation and distance measurement. With sonar objects - especially under water - can be located and measured.
• The echo sounder is basically a simple form of sonar for determining water depths, but it can also be used to detect schools of fish.
• Geophysics - to explore the subsurface z. B. to detect oil deposits, explosions or vibrations are triggered, the reflections from the underground are recorded
• various light echo processes ( lidar , laser scanner , TOF (time of flight), PMD sensor )

Application of echolocation in nature

• Main article: Echolocation (animals)
• Main article: human echolocation . Many blind people use human echolocation through technical or mechanical aids or by clicking the tongue (click sonar) to expand their perception and improve orientation.

Individual evidence

1. ↑ Hans-Werner Hunziker : Magic of hearing: Unconscious strategies of hearing perception . Transmedia Stäubli Verlag AG, Zurich 2011, ISBN 978-3-7266-0087-7 .