The waves with the frequency above the audible range of human beings are called _______.
Ultrasonic waves
Understanding Sound Waves and Frequency
Sound travels in waves. The characteristic of a sound wave that determines how high or low the sound is perceived is called its frequency. Frequency is measured in Hertz (Hz), which represents the number of wave cycles passing a point per second.
The range of frequencies that the average human ear can hear is called the audible range. This range typically falls between 20 Hz and 20,000 Hz (or 20 kHz).
Waves Above the Audible Range: Ultrasonic Waves
Waves with frequencies above the human audible range (greater than 20,000 Hz) are known as ultrasonic waves or ultrasound. Humans cannot hear these frequencies.
- Example Applications: Ultrasonic waves are used in various applications like medical imaging (ultrasound scans), cleaning equipment, sonar, and pest control.
- Animal Hearing: Many animals, such as bats, dolphins, and dogs, can hear and produce ultrasonic sounds.
Waves Below the Audible Range: Infrasonic Waves
Waves with frequencies below the human audible range (less than 20 Hz) are known as infrasonic waves or infrasound. Humans generally cannot hear these low frequencies, although very strong infrasound might be felt as vibrations.
- Examples: Infrasound can be produced by natural events like earthquakes, volcanic eruptions, avalanches, and even large animals like elephants.
Other Wave Classifications: Supersonic and Hypersonic
The terms supersonic and hypersonic are related to speed, not frequency. They describe speeds relative to the speed of sound in a medium.
- Supersonic: Refers to speeds greater than the speed of sound (Mach 1).
- Hypersonic: Refers to speeds significantly greater than the speed of sound (typically Mach 5 or higher).
These terms describe the speed of an object or a flow, not the frequency of a sound wave itself.
Analyzing the Options
Let's examine the given options based on our understanding of sound wave classifications:
- Supersonic waves: Describes speed greater than sound speed, not frequency. Incorrect.
- Ultrasonic waves: Describes waves with frequency above the human audible range. Correct.
- Infrasonic waves: Describes waves with frequency below the human audible range. Incorrect.
- Hypersonic waves: Describes speeds much greater than sound speed, not frequency. Incorrect.
Therefore, the waves with the frequency above the audible range of human beings are called Ultrasonic waves.
Revision Table: Sound Wave Classification by Frequency
| Classification | Frequency Range | Human Hearing | Examples |
|---|---|---|---|
| Infrasonic | Below 20 Hz | Cannot hear (may feel) | Earthquakes, volcanoes, elephants |
| Audible | 20 Hz to 20,000 Hz | Can hear | Human speech, music, everyday sounds |
| Ultrasonic | Above 20,000 Hz | Cannot hear | Medical ultrasound, bat echolocation, dog whistles |
Additional Information: Speed vs. Frequency
It's important not to confuse the classification of sound waves by frequency (infrasonic, audible, ultrasonic) with classifications related to the speed of objects or phenomena relative to the speed of sound (subsonic, supersonic, hypersonic).
- Subsonic: Speed below the speed of sound.
- Supersonic: Speed above the speed of sound.
- Hypersonic: Speed significantly above the speed of sound.
The speed of sound itself depends on the medium through which it travels (e.g., air, water, solids) and factors like temperature and pressure. Frequency, however, is determined by the source producing the sound.
Important Questions from Intensity and Sound Level
Which one of the following cannot be the unit of frequency of a sound wave?
The flash of lightning is seen before the thunderstorm is heard. It verifies that
The loudness of sound depends upon the
The appearance of sound to a human ear is subjectively characterized by which of the following parameters?
1. Pitch
2. Loudness
3. Quality
Choose the correct code
What is the lowest intensity of sound that a human ear can hear ?
