What are infrasonic waves?

Short Answer

Infrasonic waves are sound waves with frequencies below 20 Hz, which is lower than what the human ear can hear. These waves have very slow vibrations, so humans cannot detect them as sound, but sometimes they can be felt as gentle shaking or vibrations.

Many natural sources like earthquakes, thunderstorms, ocean waves, and volcanic eruptions produce infrasonic waves. Some animals, such as elephants and whales, use infrasonic waves to communicate over long distances because these waves can travel very far.

Detailed Explanation :

Infrasonic waves

Infrasonic waves are a special type of sound wave that have frequencies below 20 Hz. Humans can hear sounds only within the audible range of 20 Hz to 20,000 Hz. Anything below 20 Hz cannot be heard by humans, and such waves are called infrasonic waves. Even though we cannot hear them, these waves play an important role in nature and technology. They are formed when an object vibrates very slowly, producing fewer than 20 vibrations in one second.

The human ear is not sensitive enough to detect these slow vibrations. However, we may sometimes feel infrasonic waves as a deep rumble or vibration. For example, when a truck passes by or during a distant explosion, we may feel the shaking even if the sound is not clearly heard. This happens because the waves are too low in frequency to create a clear audible sensation.

Sources of infrasonic waves

Many natural and man-made sources produce infrasonic waves. Some common examples include:

  1. Earthquakes – When tectonic plates move, they release energy in the form of low-frequency waves. These waves travel long distances and are detected by seismographs.
  2. Volcanic eruptions – Explosive eruptions send out strong infrasonic waves that can be recorded thousands of kilometres away.
  3. Thunderstorms – Large storms produce low-frequency vibrations in the air.
  4. Ocean waves – The movement of large waves and storms over the sea produces infrasonic waves.
  5. Animals – Some animals communicate using infrasonic waves. Elephants use low-frequency sounds to communicate over several kilometres. Whales also use infrasonic communication in the ocean.

In addition, man-made sources like explosions, heavy machinery, rockets, and wind turbines generate infrasonic waves.

Properties of infrasonic waves

Infrasonic waves have several unique characteristics:

  • Very low frequency – Always below 20 Hz.
  • Large wavelength – Because of their low frequency, the distance between two wave peaks is large.
  • Long-distance travel – These waves can travel very far without losing much energy.
  • Low pitch – They are too low to be heard, but sometimes felt.
  • Penetration ability – They can pass through obstacles easily due to their long wavelength.

These properties make infrasonic waves useful in various scientific applications.

Applications of infrasonic waves

Although humans cannot hear infrasonic waves, scientists use them in many fields:

  1. Seismology
    Infrasonic waves play a key role in earthquake studies. Seismographs detect the infrasonic vibrations from earthquakes. This helps in predicting patterns and understanding Earth’s crust movement.
  2. Weather forecasting
    Storms, tornadoes, and hurricanes produce infrasonic signals. By studying these signals, meteorologists can predict extreme weather conditions.
  3. Animal communication study
    Researchers study infrasonic communication in animals like elephants and whales. Understanding their communication helps in wildlife conservation.
  4. Volcano monitoring
    Before a volcano erupts, it releases large amounts of low-frequency vibrations. Scientists use infrasonic detectors to monitor volcanic activity and warn nearby areas.
  5. Search and rescue operations
    Infrasonic waves generated by large movements or explosions can help locate the source of the disturbance.

Human perception of infrasonic waves

Although humans cannot hear infrasonic waves, very strong infrasonic waves may create certain sensations such as:

  • A feeling of pressure in the ears
  • Slight vibrations in the body
  • A sense of uneasiness or discomfort

These effects happen because infrasonic waves affect the body even though they do not produce an audible sound.

Difference between audible, infrasonic, and ultrasonic waves

  • Infrasonic waves → Below 20 Hz
  • Audible waves → 20 Hz to 20,000 Hz
  • Ultrasonic waves → Above 20,000 Hz

Only audible waves can be heard by humans. Infrasonic and ultrasonic waves are beyond human hearing limits.

Examples in nature

Nature produces many infrasonic waves:

  • The rumbling sound before a storm
  • Deep vibrations during an earthquake
  • Low-frequency calls of elephants
  • Ocean waves hitting against rocks
  • Wind blowing strongly during a cyclone

These examples show that even though infrasonic waves are not heard, they are present around us all the time.

Conclusion

Infrasonic waves are sound waves with frequencies below 20 Hz, too low for humans to hear. These waves are created by natural phenomena like earthquakes, storms, and ocean waves, as well as by animals and machines. Their long wavelength helps them travel long distances and carry important information. Infrasonic waves play a significant role in scientific research, weather forecasting, animal communication, and earthquake monitoring.