$A$ sound wave with frequency higher than $20 \,kHz$ is not audible for human ear. Answer the following in respect of this statement:
$(i)$ What is the term used for such a sound?
$(ii)$ Name two organisms producing sound in this range.
$(iii)$ Write an application of such a wave.

(N/A) $(i)$ The term used for sound waves with frequencies higher than $20 \,kHz$ is ultrasound.
$(ii)$ Two organisms that produce and use ultrasound are dolphins and bats.
$(iii)$ An important application of ultrasound is medical ultrasound scanning (ultrasonography) used to visualize internal body structures.