[sdiy] 555 noise!

[peter edwards]

I'm building a circuit with 4 oscillators (40106) that are volume  
modulated through transistors by pulses from 4 different 555 timers.  
That's working fine
The problem is that when all of the oscillators are turned down I can  
hear a loud click coming from the 555s.

The 4 oscillators are all mixing in a TL084 op amp.
The whole circuit is running off of a regulated 5VDC.

I thought it was coming from the transistors so I disconnected all of  
those. Still clicking.
I disconnected the output pins from the 555s altogether. Still clicking.
Added more power caps to op amp and 555s. still clicking.
It seems that the clicking is EMF coming from the 555s. I don't  
really get it though. Anybody else encounter similar problems?
should I try powering the opamp off the pre-regulated 9 volt signal?
-pete