Why do humans fail to hear very low-frequency and very high-frequency sounds? Answer the following questions.
(i) Explain, in brief, how the human ear converts sound waves within the audible range into electrical signals for the brain.
(ii) Using your explanation in part (i), give two reasons why sounds having frequencies below 20Hz and above 20kHz are not heard by an average human.
(iii) Name two animals that can detect sounds outside the human audible range and state whether the sounds they detect are infrasonic or ultrasonic.