Old time speed controls for electric motors consisted of a variable resistor that had to be perfectly matched to the motor. Silent operation, but wasted a lot of power, the heat was good for drying out a boat that might ship some water.
The first electronic variation used a power transistor instead of the resistor, and also wasted a lot of heat.
Then real ESCs hit the market using power switching to control the average current to the motor. Good control is the motor could be controlled that way, veery efficient power use, but a tendency to speak. A loudspeaker is a coil near a magnet being fed with a varying waveform and wobbling about in symathy with that wave. So is a motor, the difference being that the motor coil moves on and presents the next coil to the magnet ready for the next bit of waveform. Early ESCs ran on frame frequency, 50Hz, and the motors rumbled. Modern ESCs run at a much higher frequency because higher freqencies can use smaller components, be more compact and cost less, but the motor tends to whistle. Most operate at a frequency right in the middle of the band that human hearing works best at, a few are higher pitched so most humans don't hear it.
"Noise supression" has nothing to do with audible sounds, the "noise" is radio frequency signals that are generated by the motor as it works. The supressors isolate the motor from the wiring, which otherwise acts as a transmitter aerial, confusing the radio either by getting into the system via the receiver antenna, or being picked up by other wiring in the boat and entering the system that way.
I have had lots of success with Mtronics Viper Marine range, also Action Electronics ESCs, MR RC World controls. Which particular one depends on the model being powered. None in the cheap end of the market, but you usually only need to buy once, and their ratings are actual, rather than optimistic marks on the label, as is often the case with some ebay items.