Aerodynamic and acoustic characteristics of vocal registers were studied in profressional and non-professional singers. The air flow rate, sound intensity level and fundamental frequency were measured using SH-01 for the speech and singing voices. The rate and magnitude of vibrato were extracted from the singing voices, and an electroglottogram (EGG) was simultaneously recorded.The results were as follows : 1. In the singing mode of a professional soprano singer, the register change from “Chest” to “Mid” occurred at 350 Hz.In “Mid” register, the flow rate increased significantly even though the intensity level did not change remarkably. In the speech mode of the singers and in the singing mode of non-professional singers, the flow rate did not increase so much.2. The estimated open quotient increased when the vocal register changed from “Chest” to “Mid”. At the register changing point, the vibrato tended to be suppressed. Vibrato magnitude was significantly larger in “Mid” register than in “Chest”. There was no significant difference in vibrato rate between the two vocal registers, although it was slightly slower in “Mid” register than in “Chest”. These results suggest that the laryngeal adjustment changes so as to increase the flow rate in “Mid” register, and the change affects vibrato magnitude significantly, but not the vibrato rate.