I always find that the noise is always variable depending on the time of day if your concerned about annoying the neighbours. For some unknown reason my mag turbo is far noisier early morning and late evening yet during the day its very quite. I have a feeling though that the noise is not as loud as it sounds and you just get a bit paranoid with it, I usually play a music DVD or watch a film on my laptop at my usual volume yet my turbo does not make me have to turn the volumn up so it cannot be that loud. I am looking at cutting some thick expanded foam I have in my shed to put under the turbo as this may dampen the sound and also stop the light down stairs swinging which annoys our lass trying to watch TV
But on the brighter side of things you can gauge how well your pedalling action is by the sound, if its a wuff, wuff, wuff sound, your pedalling action is only on the down strokes, but if you get a constant hum, your pedalling a full circle.