Feedback is the name given to the terrible screeching noise caused by a sound loop being created between a microphone and a PA speaker or a guitar pickup and a guitar amplifier. While guitar players often use feedback as part of their sound, the feedback caused when a microphone is used too close to a PA speaker is less than desirable. Feedback suppressors are typically used in a live sound setting. They work by automatically locating the frequency that is causing the feedback and will make the necessary adjustments in the EQ to kill the feedback without affecting the overall sound coming through the PA. With a bunch of great products, including Behringer Feedback Suppression , Musician's Friend has the device to help you. As with everything we sell, all our Feedback Suppression equipment is supported by our price & satisfaction guarantees and free standard shipping applies to all orders except heavy items.