Echo-cardiography is used to obtain the image of

1. lungs
2. liver
3. heart
4. kidney

Elephants produce ……………sound :

1. ultrasonic
2. infrasonic
3. supersonic
4. none of the above

Choose the correct statement :

1. Ultrasonic waves travel faster than supersonic waves.
2. Sonic waves travel faster than supersonic waves.
3. Sonic waves travel faster than ultrasonic waves.
4. Sonic and ultrasonic waves travel with the same speed.

The sound of frequency less than 20 Hz is called :

1. supersonic
2. infrasonic
3. ultrasonic
4. ultrasound