The update is rolling out to US users today across the various Echo devices, as well as some third-party smart speakers that use Alexa, including the new Sonos Beam. If you have that soundbar, you could, for instance, switch to night mode to balance loud and quiet noises in a movie so you don't bother anyone else in your home late at night. Amazon is opening up the equalizer function to let developers add it to more speakers, so it could be available on other devices soon.