Although Bose pioneered noise cancelling technology, we found that masking is better for addressing noises that disturb sleep.Noise cancelling technology continuously measures, compares and reacts to outside noise, then cancels it with the opposite signal. In Bose Acoustic Noise Cancelling products, noise cancellation is combined with passive blocking to achieve a good reduction of sound at all frequencies. However, no combination of passive and active technologies for reducing the sound entering a user’s ear can make unwanted noises completely inaudible.Masking, on the other hand, introduces a soothing, desirable sound to help the brain ignore the disturbance. Masking works because of the way different sounds combine in our inner ears; if they have the right match of frequencies and the masking sound is just enough louder than the disturbing sound, the inner ear and brain cannot detect the disturbing sound. Cancellation creates quiet in our ear canals; masking—in the right conditions—creates quiet in our minds.