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.
Eyjafjallajökull is one of the smaller ice caps of Iceland. It is north of Skógar and west of Mýrdalsjökull. The ice cap covers the caldera of a volcano with a summit elevation of 1,651 metres.
The Andros Barrier Reef in the Bahamas is situated into the Tongue of the Ocean. The Tongue of the Ocean is the region of much deeper water in the Bahamas.
The Isthmus of Kra is located in the Malay Peninsula. It lies between the Ranong and Chumphon provinces of Southern Thailand. It is bordered by the Gulf of Thailand in the east and the Andaman Sea in the west.
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