Sound of frequency below 20 Hz is called:

Question

Of the following properties of a wave, the one independent of the others is:

Answer 1

Match the frequency ranges to familiar real world examples to fix the terms in memory.

Elephants and whales communicate using very low frequency sounds, well below 20 hertz, that humans cannot hear at all. Earthquakes and heavy machinery also produce vibrations in this range, and this whole very low frequency range is called infrasonic sound.
Bats and dolphins use very high frequency sounds above 20000 hertz for navigation, and medical ultrasound scans use the same high range, called ultrasonic sound.
The word supersonic describes a fast moving object, like a jet crossing the speed of sound, and has nothing to do with frequency at all.
The question asks about sound below 20 hertz, which matches the elephant and earthquake example directly.

So the correct term is infrasonic, option B.

Answer 2

Match the frequency ranges to familiar real world examples to fix the terms in memory.

Elephants and whales communicate using very low frequency sounds, well below 20 hertz, that humans cannot hear at all. Earthquakes and heavy machinery also produce vibrations in this range, and this whole very low frequency range is called infrasonic sound.
Bats and dolphins use very high frequency sounds above 20000 hertz for navigation, and medical ultrasound scans use the same high range, called ultrasonic sound.
The word supersonic describes a fast moving object, like a jet crossing the speed of sound, and has nothing to do with frequency at all.
The question asks about sound below 20 hertz, which matches the elephant and earthquake example directly.

So the correct term is infrasonic, option B.

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