We get asked this question a lot. The MRI machine uses a combination of a strong magnet, radio waves and a receiver to create images of inside the body. When the exam is performed, an electromagnet sends a current through a coiled wire. The loud clicking sound that you hear is from switching the currents on and off, which causes the coils to expand and make a banging sound. The sounds vary depending on the type of sequences being performed. Headphones with a choice of music is helpful for some patients to deal with the noise during their procedure.
It is extremely important to remember that the MAGNET IS ALWAYS ON! Every person who enters the scan room must be thoroughly screened for anything metal to ensure full safety for everyone. All equipment used in the MRI environment must be MRI compatible. Not following protocols can result in very expensive accidents, serious injury or even death.