Active noise canceling does have an adverse effect on sound quality, especially if the noise canceling isn't all that good (noise canceling can create a faint background hiss). It can mess with the purity of the sound quality so it's tricky to create a noise-canceling headphone that sounds really good. As a result, often high-end noise-canceling headphones that tout fantastic sound quality don't have as powerful noise canceling (the noise canceling feels lighter).