Noisy, 'bouncing' TRVs!?

I have TRVs fitted to most of my radiators and all of them are subject to a vibrating noise at times. I stop the noise by turning the TRV control in either direction until it stops. It has been explained to me by a plumber that the noise is due to the valve 'bouncing' when the TRV activates and, either closing or opening, is at a point where the valve is just opening or just closing. My turning the control knob then stops it by either releasing it to be more open, or shutting it altogether. Can anybody advise me as to the solution to this annoying and on-going problem? The TRVs are uni-directional, by the way, i.e. the valves are designed for the flow of water to be in one direction only rather than the more common bi-directional valves. Please help as at night the noise wakes the whole house!