Decibels of the Thomas Type Motors

The solution often employed on HO/OO gauge locomotives is to have a toothed cog attached to the driving axle(s) and then a 'worm' gear attached to the motor shaft, imagine a screw arrangement. This effectively pulls the gear round rotating the axles. The advantage to this is that it is very quiet and allows very smooth running at low speeds as well as flat out, doubly so if the motor employs a flywheel assembly to smooth out the motor operation.

The downsides are that its obviously more expensive, often the cogs/gears are made of metal and to finer tolerances than you get in Tomy trains and of course the motors are more powerful running off 12 or 16 volts depending on whether they are analog or DCC controlled.