Ultrasonic waves are high-frequency sound waves that are above the upper limit of human hearing. In order to produce these waves, a specific material is required.

Option 1: Ferromagnetic material is a material that exhibits a strong magnetic field. However, it is not used for producing ultrasonic waves.

Option 2: Ferrimagnetic material is also a magnetic material, but like ferromagnetic material, it is not used for generating ultrasonic waves.

Option 3: Piezoelectric material is the correct answer. Piezoelectric materials have the property of generating an electric charge when subjected to mechanical stress or pressure. This property makes them ideal for generating ultrasonic waves. When an electric voltage is applied to a piezoelectric material, it vibrates at a very high frequency, producing ultrasonic waves.

Option 4: Pyroelectric material, on the other hand, generates an electric charge when there is a change in temperature. While pyroelectric materials can be used in some applications, they are not primarily used for producing ultrasonic waves.

Therefore, the correct answer is option 3 - piezoelectric material.