Physics

3.7 - Infrasound

2 min

note 1 of 2

Infrasound is sound below 20 Hz

Humans can hear sound across a range of frequencies from about 20 Hz up to 20,000 Hz.
Infrasound is sound with a frequency below 20 Hz.
Infrasound sits at the opposite end of the frequency range to ultrasound, which is sound above 20,000 Hz.

note 2 of 2

Some animals (such as elephants and whales) communicate using infrasound calls that travel over long distances.
Detecting this infrasound allows scientists to track these animals for conservation purposes.

Natural events such as erupting volcanoes, avalanches, and earthquakes produce infrasound.
Monitoring this infrasound helps scientists predict events, such as whether a volcano is about to erupt.

Earthquakes produce waves with frequencies below 20 Hz that travel through the layers of the Earth.
Because these waves pass deep through the planet, they can be used to explore the internal structure of the Earth.

key terms

TermDefinition

InfrasoundSound with a frequency below 20 Hz.

UltrasoundSound with a frequency higher than 20,000 Hz, which is above the limit of human hearing.

end of notes

Uses and natural sources of infrasound

Animal communication

Some animals (such as elephants and whales) communicate using infrasound calls that travel over long distances.

Detecting this infrasound allows scientists to track these animals for conservation purposes.

Monitoring natural events

Natural events such as erupting volcanoes, avalanches, and earthquakes produce infrasound.

Monitoring this infrasound helps scientists predict events, such as whether a volcano is about to erupt.

Exploring the Earth's structure

Earthquakes produce waves with frequencies below 20 Hz that travel through the layers of the Earth.

Because these waves pass deep through the planet, they can be used to explore the internal structure of the Earth.