Three different vibrating objects produce three types of sounds X, Y and Z.
Sounds X and Y cannot be heard by a man having normal range of hearing but sound Z can be heard easily.
The sound X is used for echocardiography.The sound similar to that which is produced during an earthquake before the main shock wave is generated.
Name one device in a science laboratory which can produce sound like Y.
The correct option is A simple pendulum.
Ultrasound is used in echocardiography. In this ultrasound are used to construct the image of heart. Ultrasounds and infrasounds are not audible to man. Ultrasound have frequency more than 20 kHz.
Infrasound have frequency below 20 Hz.
Y is infrasound .