What is Infrasonic Wave?

S6-SA3-0230

Grade Level:

Class 10

AI/ML, Physics, Biotechnology, Space Technology, Chemistry, Engineering, Medicine

Definition

What is it?

An infrasonic wave is a sound wave that has a frequency lower than the human ear can hear. Humans can typically hear sounds between 20 Hertz (Hz) and 20,000 Hz, so infrasonic waves are those with frequencies below 20 Hz.

Simple Example

Quick Example

Imagine your father's old radio playing music. If you slowly turn down the 'bass' knob, you're reducing the low-frequency sounds. Infrasonic waves are like extremely deep bass notes, so low that even if the radio could produce them, you wouldn't hear them, but you might feel a rumble.

Worked Example

Step-by-Step

Let's say a sound wave has a frequency of 15 Hz. Is it an infrasonic wave?
---Step 1: Recall the human hearing range. Humans can hear sounds with frequencies from 20 Hz to 20,000 Hz.
---Step 2: Compare the given frequency with the lower limit of human hearing.
---Step 3: The given frequency is 15 Hz.
---Step 4: Since 15 Hz is less than 20 Hz, it falls below the human hearing range.
---Answer: Yes, a sound wave with a frequency of 15 Hz is an infrasonic wave.

Why It Matters

Understanding infrasonic waves is crucial in fields like seismology for earthquake prediction, and in medicine for diagnosing certain conditions. Engineers use this knowledge to design structures that can withstand vibrations, and it even helps in space technology to study atmospheric phenomena.

Common Mistakes

MISTAKE: Confusing infrasonic waves with ultrasonic waves. | CORRECTION: Infrasonic waves are below human hearing (less than 20 Hz), while ultrasonic waves are above human hearing (greater than 20,000 Hz).

MISTAKE: Believing that infrasonic waves cannot exist because humans can't hear them. | CORRECTION: Infrasonic waves exist naturally (e.g., from earthquakes, volcanoes) and can be produced artificially, even if we can't perceive them with our ears.

MISTAKE: Thinking infrasonic waves are always very loud or destructive. | CORRECTION: While some infrasonic waves (like from explosions) can be powerful, their 'loudness' is separate from their frequency. Many natural infrasonic waves are very subtle.

Practice Questions

Try It Yourself

QUESTION: A sound wave has a frequency of 10 Hz. Is it infrasonic, audible, or ultrasonic? | ANSWER: Infrasonic

QUESTION: An elephant communicates using sounds around 12 Hz. What type of sound wave is this? How does it compare to human hearing? | ANSWER: This is an infrasonic wave. Humans cannot hear it because it is below our lower hearing limit of 20 Hz.

QUESTION: If a sound wave travels at 340 m/s and has a wavelength of 20 meters, calculate its frequency. Is this an infrasonic wave? (Hint: Speed = Frequency x Wavelength) | ANSWER: Frequency = Speed / Wavelength = 340 m/s / 20 m = 17 Hz. Yes, this is an infrasonic wave because 17 Hz is less than 20 Hz.

MCQ

Quick Quiz

Which of the following frequencies represents an infrasonic wave?

25 Hz

1500 Hz

10 Hz

25000 Hz

The Correct Answer Is:

Infrasonic waves have frequencies below 20 Hz. Out of the given options, only 10 Hz is below 20 Hz. 25 Hz and 1500 Hz are audible, and 25000 Hz is ultrasonic.

Real World Connection

In the Real World

Infrasonic waves are used by meteorologists to track severe weather events like cyclones and thunderstorms, as these events generate low-frequency sounds that travel long distances. Scientists at ISRO might even use similar principles to monitor atmospheric changes from space.

Key Vocabulary

Key Terms

FREQUENCY: The number of wave cycles passing a point per second, measured in Hertz (Hz). | HERTZ (Hz): The unit of frequency, representing one cycle per second. | AUDIBLE RANGE: The range of sound frequencies that humans can typically hear (20 Hz to 20,000 Hz). | ULTRASONIC WAVE: A sound wave with a frequency above the human hearing range (greater than 20,000 Hz).

What's Next

What to Learn Next

Now that you understand infrasonic waves, you can explore ultrasonic waves next. Learning about them will help you see the full spectrum of sound and how different animals and technologies use these 'silent' sounds.