Acoustic underwater telephony

from Wikipedia, the free encyclopedia

Acoustic underwater telephony is a method of underwater communication in which sound is used as a transmission medium.

Basics

A hydrophone is due to poor propagation of electromagnetic waves, particularly in saltwater an acceptable alternative to communication. The absorption coefficient of sound is less than 5 dB / km below 20 kHz and decreases sharply with decreasing frequency.

Today, sound transducers are based on the piezo effect , and in the past also on the magnetostrictive effect. See also underwater microphone and underwater loudspeaker .

System Gertrude

The system was introduced and practiced between German submarines during World War II and was known here under the code name Gertrude . The speech signal was shifted to a higher frequency range via amplitude modulation in order to achieve a better signal-to-noise ratio. It was a single sideband modulation (upper sideband) with 9 kHz carrier frequency. The frequency band commonly used in telephony, 300 Hz to 3 kHz, was transmitted. In particular in shallow water, the reception was extremely poor because of the multipath propagation . Only this one frequency channel was available. The range was very limited and dependent on the water depth and temperature . Gertrude didn't work through the thermocline . In the meantime, underwater communication is used in the frequency range from 10 Hz to 1 MHz with ranges of up to 1000 km. The low available bandwidth, the long latency, the multipath propagation, the attenuation, the dispersion and the Doppler effect interfere with the transmission and often only allow short ranges and data rates.

Applications in the present

Today, for example, underwater telephony between divers using ultrasound is common. In addition to voice communication, data transmission is the main area of ​​application for underwater communication. In addition to primarily military applications, the tsunami early warning system GITEWS should be mentioned , which consists of a pressure sensor network on the sea floor. The Deep Siren communication system promises a range of a few 100 kilometers.

See also

Individual evidence

  1. ↑ a b https://www.net.in.tum.de/fileadmin/TUM/NET/NET-2011-07-1/NET-2011-07-1_07.pdf M. Grimm: Acoustic underwater communication , work on the TU Munich, July 2011, page 45
  2. ↑ A. Quaz, W. Konrad: Underwater acoustic communications - UQC-1B "Gertrude", IEEE Communications Magazine, Volume 20 Issue, March 2, 1982, pages 24–30, IEEE Press Piscataway, NJ, USA doi : 10.1109 / MCOM.1982.1090990
  3. ↑ AKYILDIZ, IF; POMPILI, D.; MELODIA, T .: "Underwater acoustic sensor networks: research challenges" in Ad Hoc Networks 3 (2005), No. 3, pp. 257-279
  4. ↑ http://www.profrie-dive.de/produktdetails/product/ultraschall-kommunikation-ocean-reef-gsm-dc.html Message from Wolfgang Friebe / Profrie-Dive
  5. ↑ Deep Siren holds key to US submarine communications problem  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. www.defensenews.com@1@ 2Template: Dead Link / www.defensenews.com  
  6. ↑ Manufacturer's brochure ( Memento from July 31, 2009 in the Internet Archive )