Ultrasound refers to a sound wave with a frequency greater than the upper limit of human hearing, which is generally over 20 kHz. In general, humans can hear sounds with a frequency between 20 Hz and 20 kHz.
Oceanic trenches are long and narrow depressions of the sea floor. They are the deepest parts of the ocean floor. They are a type of tectonic landforms.Horst is a raised fault block bounded by normal faults. The word Horst in Dutch and German means ‘heap’. It is a raised block of earth’s crust that has been lifted. It is a tectonic landform.
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