Not effective against high and low range sounds
The device works as described, but unfortunately was ineffective against the problem I was trying to solve.  If the noise you want to block out is in a mid-range frequency (for instance constant engine noise, or music in another room), this will probably work well for you.  But my issue is the sound of garbage pick-up outside my NYC windows.  The high-frequency clinking of glass and the low-frequency truck noises cut right through the white noise.  I returned it.
Rating: 3 stars