The effects of gear intermeshing conditions such as load torque and mesh angle on gear noise were studied experimentally. In spite of the fact that the gear noise has been investigated for a long time by many researchers, the problem on the gear noise is still a matter of primary concern for motorcycle drivers, and it may control the motorcycle market. According to previous several excellent papers, it was shown that the intermeshing conditions greatly affect the quality of gear noise, but the relation between them has not revealed clearly. The purpose of this study is to find the effects of intermeshing condition on the gear noise. We designed and constructed a small size model of rotor system connected by a pair of gears, and measured the sound pressure around the intermeshing area. As a result, several higher harmonic frequencies due to tooth mesh frequency were observed, and spectrum level of these frequencies might be changed by the mesh angle. It may be possible to estimate the intermeshing condition by evaluating gear noise and comparing the noise level at each harmonic frequency of tooth mesh frequency.