Answers

2016-01-02T14:58:36+05:30
Infrasound, sometimes referred to as low-frequency sound, is sound that is lower in frequency than 20 Hz hertz or cycles per second, lower than the "normal" limit of human hearing
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2016-01-02T16:06:08+05:30
Speed of Infrasonics:  >20hz.
Humans can only hear more than 20hz.
Examples of Infranasonics are DOLPHIN,ELEPHANT

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