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.
Mertz Glacier is located in the continent of Antarctica. It is about 45 miles long, heavily crevassed glacier in George V Coast of East Antarctica. The extension of this glacier into the Southern Ocean is called the Mertz Glacial Tongue.