Echo , or excessive reverberation, can be the result of poor architectural design or timing variations between speakers. Timing problems occur in large rooms in which speakers face each other from different sides of a room. If a church has a long, narrow sanctuary and puts a speaker on the back wall, that speaker should have a slight sound delay. Otherwise, the sound waves from the front speaker will arrive at the back of the sanctuary after the rear speaker releases its waves. It's easier to place all of the speakers at the front of a room and adjust their volume and position to reach the back row.
Some buildings have flat, reflective surfaces that make sound waves act like bumper cars.
For example, if a church holds a potluck dinner in a gymnasium or multipurpose facility with hard surfaces, table conversation will become a muddy hum that gradually increases in volume. A speaker's voice will bounce around the room. This problem can be remedied by hanging fabric panels, banners, or baffles on the walls or from the ceiling. Feedback occurs when amplified sound from a speaker or monitor circulates through a microphone and is amplified again, giving off an obnoxious squeal. This kind of sound loop is due to monitor placement as well as microphone technique.