DS1 was/is spirited and we have ALWAYS used white noise to help him sleep. We also keep his room really dark with dark blue shades. We run a small desk fan on high (point it away from him so he does not get too cold). It is a great sleep cue for them too. Now at 3 1/2, he actually turns it on himself before his nap and bedtime. We run it the entire time he is sleeping. I don't think it is necessary to buy a machine dedicated to white noise. You can use a fan, radio, CD.
HTH!
xxx
Judy