In the ferromagnetic materials magnetomechanical acoustic emission (MAE) is produced through magnetomechanical coupling between spin motion of domain wall and internal lattice strain when the $180^\circ$ domain wall nucleation and annihilation happen. The rms voltage, V, and the wave form of MAE of grain-oriented 3% Si-Fe polycrystal are measured for 6 values of the angle, Φ, between rolling direction and magnetizing direction with various frequencies and amplitudes. Their 6 values for these measurements are $0^\circ$, $35^\circ$, $45^\circ$, $55^\circ$, $70^\circ$, and $90^\circ$. It is found that the intensity of MAE signal is active at the domain nucleation and annihilaton part in B-H loop. When Φ is increased up to $45^\circ$, the rms voltage decreases, but increasing Φ furthermore it increases and has its maximum value at $Φ=55^\circ$. And increasing Φ furthermore from $55^\circ$, the rms voltage decreases again. The rms voltage increases with increasing of frequency, f, and amplitude, H, of magnetizing field. Also it is found that the specimens with $0^\circ$ and $55^\circ$ which have small $H_c$ (coercive force) have much larger V than others. The experimental result for the expression of rms voltage dependence is 0.13 $(Hf/H_c)^{0.3}$. This result agreeswith the theoretically treated result developed in this work.
