Does anyone know the point of the "Whisper Quiet" upgrade?

I think it makes the machine run a bit quieter. I remember giving this upgrade to one of my sims but she was living alone in a house, so I didn't notice other effects. I do have a sim living in San Myshuno and her neighbour is almost everyday knocking on her door because of the noise, but she doesn't use the machine that often, think it's because of the radio.