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Several aquatic bird species have been observed to react to underwater sound in the 1-4 kHz range, [49] which follows the frequency range of best hearing sensitivities of birds in air. Seaducks and cormorants have been trained to respond to sounds of 1-4 kHz with lowest hearing threshold (highest sensitivity) of 71 dB re 1 μPa [ 50 ...
SOFAR channel. Underwater sound speed as a function of depth. Data derived from readings taken north of Hawaii in the Pacific Ocean and sourced from the World Ocean Atlas, 2005 edition. Note the SOFAR channel axis at ca. 750 m depth, where sound speed is shown at its lowest. The SOFAR channel (short for sound fixing and ranging channel), or ...
Underwater acoustic communication is a technique of sending and receiving messages in water. [1] There are several ways of employing such communication but the most common is by using hydrophones. Underwater communication is difficult due to factors such as multi-path propagation, time variations of the channel, small available bandwidth and ...
Communication with submarines is a field within military communications that presents technical challenges and requires specialized technology. Because radio waves do not travel well through good electrical conductors like salt water, submerged submarines are cut off from radio communication with their command authorities at ordinary radio frequencies.
Alternative definitions. ELF is a subradio frequency. [14] Some medical peer reviewed journal articles refer to ELF in the context of "extremely low frequency (ELF) magnetic fields (MF)" with frequencies of 50 Hz [15] and 50–80 Hz. [16] United States Government agencies, such as NASA, describe ELF as non-ionizing radiation with frequencies ...
Bloop was an ultra-low-frequency, high amplitude underwater sound detected by the U.S. National Oceanic and Atmospheric Administration (NOAA) in 1997. [1] By 2012, earlier speculation that the sound originated from a marine animal [2] was replaced by NOAA's description of the sound as being consistent with noises generated via non-tectonic ...
Infrasound, sometimes referred to as low frequency sound, describes sound waves with a frequency below the lower limit of human audibility (generally 20 Hz, as defined by the ANSI/ASA S1.1-2013 standard). [1] Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be ...
Bloop is the name given to an ultra-low-frequency and extremely powerful underwater sound detected by the U.S. National Oceanic and Atmospheric Administration (NOAA) in 1997. The sound is consistent with the noises generated by icequakes in large icebergs, or large icebergs scraping the ocean floor. [3]