Dohm-SS Single Speed Sound Conditioner
I bought this for my infant to help block out other noise when he sleeps, especially when traveling and staying in hotel rooms or new settings.  It has worked well and the only reason I'm giving it 4 instead of 5 stars is because it's louder than I thought it would be.  However, it works exactly as advertised and really drowns out any other noise.
Rating: 4 stars