We give the analytical expressions for the transfer of amplitude noise from the mixing frequencies to the generated frequencies during a nondegenerate and partially degenerate four-wave mixing (FWM) process and verify them by comparing with the numerical simulation results. We use these analytical expressions to study the amplitude noise relationships between the mixing frequencies and the generated frequencies during an FWM process, for various conditions. We also study the variance, relative intensity noise (RIN), and signal-to-noise ratio (SNR) of the generated frequencies as a function of the power, RIN, and SNR of the input signal. (C) 2017 Optical Society of America