Abstract: Based on the damped motion of air medium equation, the quality factor of energy dissipation is de- fined, the solution of stable equation is obtained without the forcing underdamped condition. The mechanical energy formula of system stored in the time t is derived, and the relationship between the quality factor and the related parameters is got. According to the maximum amplitude of the system reaching steady amplitude and the system resonance, the half broadband relationship is deduced. Through the establishment of forcing power （P1） and resistance （P2） expression formula, the conclusion two equal size minus opposite, namely, P1 ＋P2 =0, are obtained, with t to （t＋T） for solving the integral upper limit and lower limit of average power, and the result are got that force work is equal to the system to add energy. The discussion of these issues can play guiding role for colleagues and students.

Key words: Bobr resonance experiment, quality factor, half broadband, forcing and damping of power, theoretical discussion