The first step we are going to take before delving fully into the meaning of the term infrasound is to know its etymological origin. In this case, we can state that it is a word that derives from Latin, it is exactly the result of adding several lexical components of said language:
-The prefix “infra-”, which is synonymous with “below”.
-The verb “sonare”, which is equivalent to “cause sound”.
-The suffix “-ido”, which is used to indicate the quality that is perceptible by the senses.
Infrasound is a notion that is used in the field of physics . This is the name given to the sound wave that, due to its low vibration frequency , is not detected by the human ear .
Let us remember that a wave is a periodic movement whose propagation can take place in a vacuum or in a physical medium. In the case of sound waves , they are produced by the vibration of a physical element and transmit a sound .
The vibration of adjacent molecules generates a chain movement that, when propagated, causes pressure differences that the human ear perceives as a sound . A person's ear can register sound waves with frequencies between approximately 20 Hz and 20,000 Hz.
This means that sound waves with a frequency lower than 20 Hz are not detected by humans: these are infrasounds that we do not hear. Many animals , such as whales , tigers and elephants , do pick up waves of this type.
The hippopotamus, the crocodile and even the rhinoceros are considered to be other animals capable of appreciating these waves, that sound that is not perceptible to the human ear.
No less interesting is knowing that even the earth is capable of producing what are those low frequency waves that concern us. Specifically, this is something that occurs when an earthquake occurs. And precisely because there are animals that are capable of appreciating these waves, they are capable of knowing that an earthquake is coming before it is perceptible to humans.
Likewise, we have to know that, although man is not capable of perceiving infrasound, he can endure adverse consequences from it. A good example of this is that it can be caused by a car, a plane or even a boiler and, although a person does not notice it, it is possible that they will have to face consequences of this such as a headache, vertigo or even nausea.
It should be noted that Hz is the symbol for hertz , the unit that reflects the amount of vibrations per unit of time: that is, the frequency . When the frequency is low (and, therefore, the sound wave presents few vibrations per time unit), it is an infrasound that humans cannot hear.
If the sound wave has a very high frequency , greater than 20,000 Hz , it is called ultrasound . As with infrasound, humans cannot perceive them either, unlike bats , dolphins and other species.