Ultrasonic and Infrasonic Waves, and Their Applications
Introduction
Humans can hear only a limited range of sound frequencies. This range is called the audible range or human hearing range.
Human audible range = 20 Hz to 20 kHz
Sound waves with frequencies below or above this range cannot be heard by humans. However, such sound waves are very useful in science, medicine and technology.
Types of Sound Waves Based on Frequency
On the basis of frequency, sound waves can be divided into three main types:
| Type of Sound Wave | Frequency Range | Can Humans Hear? |
|---|---|---|
| Infrasonic waves | Less than 20 Hz | No |
| Audible sound waves | 20 Hz to 20 kHz | Yes |
| Ultrasonic waves | More than 20 kHz | No |
Infrasonic Waves
Sound waves with frequencies less than 20 Hz are called infrasonic waves.
Humans cannot hear infrasonic waves because their frequency is below the human audible range.
Applications of Infrasonic Waves
- Infrasonic waves are used for detecting natural events such as earthquakes.
- They are used for detecting volcanic eruptions.
- They are also used for detecting severe storms.
- These waves are useful because they can travel long distances through air and the Earth.
Ultrasonic Waves
Sound waves with frequencies more than 20 kHz are called ultrasonic waves.
Humans cannot hear ultrasonic waves because their frequency is above the human audible range.
Applications of Ultrasonic Waves
- Ultrasonic waves are used for imaging internal organs without surgery. This is called ultrasonography.
- They are used for breaking kidney stones into smaller pieces, which can then pass out of the body.
- They are used for ultrasonic welding.
- They are used for cleaning delicate machine parts in industries.
- They are used for detecting defects inside metal blocks during construction and industrial testing.
- They are used for locating objects when sound waves get reflected from them.
Diagram: Sound Waves Based on Frequency
Explanation of the Diagram
The diagram shows the classification of sound waves according to frequency. Sounds below 20 Hz are infrasonic waves. Sounds between 20 Hz and 20 kHz are audible to humans. Sounds above 20 kHz are ultrasonic waves.
Comparison of Infrasonic and Ultrasonic Waves
| Basis | Infrasonic Waves | Ultrasonic Waves |
|---|---|---|
| Frequency | Less than 20 Hz | More than 20 kHz |
| Human hearing | Cannot be heard by humans | Cannot be heard by humans |
| Main use | Detecting natural events | Medical and industrial applications |
| Examples | Earthquakes, volcanic eruptions, severe storms | Ultrasonography, kidney stone treatment, welding, cleaning, defect detection |
Use of Ultrasonic Waves in Medicine
Ultrasonic waves are very useful in medicine because they can help in studying internal organs without surgery.
This method is called ultrasonography. It helps doctors form images of internal organs.
Ultrasonic waves are also used to break kidney stones into smaller pieces. These smaller pieces can then pass out of the body.
Use of Ultrasonic Waves in Industries
Ultrasonic waves are also useful in industries.
- They are used in ultrasonic welding.
- They are used for cleaning delicate machine parts.
- They are used for detecting defects inside metal blocks.
This is useful during construction and industrial testing because internal defects may not be visible from outside.
Use of Sound Waves for Locating Objects
Sound waves can reflect from objects. This property is used to locate objects.
When ultrasonic waves are sent towards an object, they reflect back. By studying the reflected waves, the position of the object can be found.
This idea is important in applications such as echolocation and sonar, which will be studied in the next topics.
Why These Waves are Important
Even though humans cannot hear infrasonic and ultrasonic waves, they are very useful.
- Infrasonic waves help in studying natural events.
- Ultrasonic waves help in medical diagnosis and treatment.
- Ultrasonic waves help in industrial cleaning, welding and testing.
- Reflected ultrasonic waves help in locating objects.
Important Terms
1. Audible Range
The range of frequencies that humans can hear is called the audible range. It is from 20 Hz to 20 kHz.
2. Infrasonic Waves
Sound waves with frequencies less than 20 Hz are called infrasonic waves.
3. Ultrasonic Waves
Sound waves with frequencies more than 20 kHz are called ultrasonic waves.
4. Ultrasonography
The use of ultrasonic waves for imaging internal organs without surgery is called ultrasonography.
5. Ultrasonic Welding
The use of ultrasonic waves for welding materials is called ultrasonic welding.
Important Points
- Humans can hear sounds only from 20 Hz to 20 kHz.
- Sound waves below 20 Hz are called infrasonic waves.
- Sound waves above 20 kHz are called ultrasonic waves.
- Infrasonic and ultrasonic waves cannot be heard by humans.
- Infrasonic waves are used for detecting earthquakes, volcanic eruptions and severe storms.
- Ultrasonic waves are used in ultrasonography.
- Ultrasonic waves are used for breaking kidney stones into smaller pieces.
- Ultrasonic waves are used for ultrasonic welding and cleaning delicate machine parts.
- Ultrasonic waves are used for detecting defects inside metal blocks.
- Ultrasonic waves can be used to locate objects by studying reflected sound waves.
Conclusion
Infrasonic and ultrasonic waves are sound waves outside the human audible range. Infrasonic waves have frequencies less than 20 Hz, while ultrasonic waves have frequencies more than 20 kHz. Humans cannot hear these waves, but they have many important uses. Infrasonic waves help in detecting natural events, while ultrasonic waves are used in medicine, industries and object detection.
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