Ultrasonic and Infrasonic Sound

How are dogs made alert by the crime department? Explain.

Give suitable reasons, as to why sound cannot be heard in the following cases:

The sound produced by a Galton whistle.

Give suitable reasons, as to why sound cannot be heard in the following cases:

A simple pendulum executing $10$ oscillations in one second.

Which of the following statements is wrong?

The sounds of frequencies greater than $20 \mathrm{kHz}$ are called ultrasonic sounds.

_____ sound is used as a diagnostic tool in medical science.

How do bats and whales make use of ultrasonic sounds?

What is sonography?

State any three uses of ultrasonic sound.

What is an echo?