It works for me. Its not directly tied to speed, like old systems used to be (which assumed noise levels would rise as you go faster). It uses the microphones in the overhead console, to monitor the cabin noise level. They are repairing the roads near my house, and so all the road has been scraped down. Its very loud when driving on it. When I turn onto that from the regular road surface, the volume increase is very noticeable. When just cruising around suburban roads its not very noticeable, and that is kind of the point -- the noise level doesn't change much in those conditions. If you listen to the music very loudly, there may be a point at which it won't increase it anymore (to prevent hearing loss). Finally, it does more than just change the volume, which isn't always a good thing. It tries to boost the sound in the range of frequencies where the ambient noise is coming from, akin to the same Bose technology they use in their headphones. Most of the time this works, but I've found with certain songs the sound shaping results in parts of the music become harder to hear when it messes with the sound.