Range of Hearing in Humans MCQs Quiz | Class 9
This Class IX Science quiz (Unit III: Motion, Force and Work) tests your understanding of the audible range, infrasound, and ultrasound limitations. Topics covered include the frequency limits of human hearing and examples of animals using different frequency ranges. Attempt these 10 MCQs, check your score, and download the solution PDF for revision.
Overview of Human Hearing Range
In the study of Sound for Class 9 Science, understanding the range of hearing is fundamental. The human ear is sensitive only to a specific band of frequencies. Sounds outside this band are inaudible to us, even if they are very loud. This limitation defines our “audible range.”
Key Concepts
- Audible Range: For an average human being, the audible range of frequencies is from 20 Hz to 20,000 Hz (20 kHz).
- Infrasonic Sound (Infrasound): Sounds with frequencies below 20 Hz. Humans cannot hear them, but they can be felt as vibrations. Examples include sounds produced by earthquakes, volcanoes, and certain animals like whales, elephants, and rhinoceroses.
- Ultrasonic Sound (Ultrasound): Sounds with frequencies higher than 20,000 Hz. Humans cannot hear them. Animals like dogs, bats, dolphins, and porpoises use ultrasound for navigation and communication.
- Age Factor: The upper limit of hearing (20 kHz) often decreases with age. Children under the age of 5 can hear up to 25 kHz.
Comparison of Frequency Ranges
| Category | Frequency Range | Examples/Remarks |
|---|---|---|
| Infrasonic | Less than 20 Hz | Rhinoceros (5 Hz), Whales, Elephants, Pendulums |
| Audible | 20 Hz to 20,000 Hz | Human speech, music, general noise |
| Ultrasonic | Greater than 20,000 Hz | Bats, Dolphins, Rats, Moths |
Quick Revision Points
- Hz is the unit of frequency (Hertz).
- Rhinoceroses communicate using infrasound as low as 5 Hz.
- Bats use ultrasonic squeaks to locate prey and navigate in the dark (Echolocation).
- Earthquakes produce low-frequency infrasound before the main shock waves begin.
Extra Practice Questions
- Q: Why do some animals get disturbed before an earthquake?
Ans: Because they can hear the infrasound produced by the quake before the main shockwaves arrive. - Q: Can a simple pendulum produce audible sound?
Ans: No, it typically oscillates at a frequency below 20 Hz (infrasound). - Q: What is the frequency limit for dogs?
Ans: Dogs can hear up to approximately 45-50 kHz. - Q: What happens to the audible range as people get older?
Ans: The ability to hear high-frequency sounds diminishes. - Q: How do moths escape from bats?
Ans: Certain moths can hear the high-frequency squeaks of bats and fly away to escape.
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