Self exciting oscillation in gas fired appliances leads to abnormal combustion noise which is focused in this work. For studying this phenomena and modeling abnormal combustion noise a simple hand made instrument was made. Then the property of fundamental parts of unit is studied and also some practical methods for reducing the loud noise are given. These methods are based on modification of the fundamental parts of unit. The mathematical model of this phenomenon is illustrated and also the stability criteria for the unit based on this model is given. Then the effect of changing excitation point in this phenomenon is studied and finally the experimental stability diagram based on modification on fuel/air ratio is given.