In this study, emission rates of aerosols emitted by professional singers were measured with a laser particle counter under cleanroom conditions. The emission rates during singing varied between 753.4 and 6095.37~P/s. Emission rates for singing were compared with data for breathing and speaking. Significantly higher emission rates were found for singing. The growth rates between singing and speaking were between 3.97 and 99.54. Further, effects of vocal loudness and gender were investigated. The present study should support the efforts to improve the risk management in cases of possible aerogenic virus transmission, especially for choir singing.