The correct option is (c).
Explanation
Sound waves are classified based on their frequency relative to the range of human hearing. The audible range for humans is approximately 20 Hz to 20,000 Hz (20 kHz).- Statement 1 is Incorrect: Infrasound refers to sound waves with frequencies below 20 Hz. Frequencies higher than 20,000 Hz are known as ultrasound. Therefore, the definition provided in the statement applies to ultrasound, not infrasound.
- Statement 2 is Correct: Earthquakes produce low-frequency infrasound before the main shock waves (seismic waves) propagate. This characteristic allows certain animals, which are sensitive to these low frequencies, to detect an impending earthquake before it is perceptible to humans.
- Statement 3 is Correct: Rhinoceroses communicate using infrasound with frequencies as low as 5 Hz. This ability is also observed in other animals, such as whales and elephants, allowing for communication over long distances.
Key Takeaway: Infrasonic sound (Infrasound) consists of frequencies below 20 Hz and is associated with natural phenomena like earthquakes and volcanoes, as well as communication in large mammals like rhinoceroses and elephants.