Pull the connector on the speed control deactivation switch, and test it for continuity with a meter.
With the brake pedal off, the switch should be closed, or show less than 100 ohms of resistance ( if you have good batteries in your meter, it should be much lower ).
Making sure not to let the meter probes fall off, try to move the brake pedal side to side, and see if the switch opens. It could be a faulty deactivation switch that allows the switch to open while you are driving.
When you hear the noise after this happens, are there any driving issues ( throttle drops off, truck shuts down, etc ) ?
Hoping the issue is with the deactivation switch. If you have to replace it, be careful not to press the switch, or press on the brake pedal when installing it.
The switch self adjusts, and if the switch moves while installing it, you will need another one ( only get one self adjustment out of a new switch ).