Rhinoceroses communicate using infrasonic waves of frequency as low as 5 Hz. 

Time between transmission and direction, t = 3.42 s

Speed of ultrasound in sea water, v = 1531 m/s 

Let, the depth of the sea be 'd'. 

Distance travelled by the ultasound = 2 x depth of the sea = 2d 

Therefore,
                2d  = speed of sound X time

                      = 1531 m/s x 3.42 s

                      = 5236 m  

Therefore,

Distance of the seabed from the ship, d =$\frac{5236}{2} = 2618 m = 2.62 km$

Thus, the distance of the seabed from the ship is 2.62 km. 

Given, 

Time between transmission and detection of sonar pulse, = 1.02 s  

Speed of sound in salt water, v=  1531 ms^-2

Let, distance of the cliff be equal to d (say).

Then the distance travelecd by sound = 2d 

Now, using the distance-time formula, we have

            2d = speed of sound x time

                 = vt 

                 = 1531 x 1.02 m 



So, distance of the cliff, d = $\frac{1531\times 1.02}{2} = 780.81 m$

When the earth quakes, they produce low frequency infrasound before the main shock waves. These infrasonic waves are not audible to the human ears. But animals are able to detect these waves and hence some animals get disturbed before earthquakes and start behaving in a different manner.

A battery operated electronic device used by persons who cannot hear properly is called as hearing aid. 

Working of the hearing aid is as follows:

Hearing aid receives sound through a microphone. The microphone converts the sound waves to electrical signals. These electrical signals are amplified by an amplifier. The amplified electrical signals are given to a speaker of the hearing aid. The speaker converts the amplified electrical signal to sound and sends to the ear for clear hearing.