Question

Which of the following frequencies of sound elephants produce?

Answer 1

Hint: Soundwaves can be categorized into three types based on the frequencies, i.e., infrasonic, ultrasonic, and audible to human ears. Humans’ ears are not evolved to hear the infrasonic and ultrasonic soundwaves. Humans can only hear soundwaves in the frequency range of $20Hz$ to $20000Hz$.

Complete solution:
Sound waves are longitudinal waves that propagate through the air media with the simultaneous change in pressure in the medium. That is why, unlike light waves, sound waves can not propagate through the vacuum. The frequency of soundwaves varies in a vast range.
Depending on the frequency of the soundwaves, one can categorize them into three different categories, and two out of them are not audible to human ears, i.e., infrasonic and ultrasonic soundwaves. The lowest limit of human hearing is $20Hz$, and the highest limit of human hearing is about $20000Hz$. The infrasonic sounds have frequencies less than $20Hz$ , and the ultrasonic sound waves have frequencies greater than $20000Hz$.
How many animals in this world can produce both ultrasonic sound waves and infrasonic sound waves. Dogs, bats, and dolphins can produce ultrasonic sound waves in order of their communication and survival.
Now, elephants’ vocalization is evolved to make infrasonic sound waves, also inaudible to human ears. The elephants use low-frequency sound waves to communicate because soundwaves of that frequency can travel faster than the usual soundwaves suitable to human hearing.

Note: In an ideal laboratory, experiment a human can hear up to $28KHz$, but in general, humans can only hear up to soundwaves of frequencies $15KHz$ to $17KHz$. Ultrasonic soundwaves are very useful to humans. In the medical field, ultrasound is used for ultrasonography, i.e., making images with ultrasound, and in the navy, we use SONAR, i.e. sound navigation ranging.