While heat styling is always damaging to hair to some degree, it's true that our Lab tests found that the Dyson Supersonic operated about 10°F lower than the average hair dryer, so of all hair dryers, it's the least damaging option we've tested. While Dyson has claimed that the Supersonic hair dryer is quieter than the competition (keep in mind that "supersonic" means "greater than the speed of sound"), both our Lab tests and consumer tests found that the hair dryer is about as noisy as other hair dryers. While Dyson has claimed that the Supersonic hair dryer is quieter than the competition (keep in mind that "supersonic" means "greater than the speed of sound"), both our Lab tests and consumer tests found that the hair dryer is about as noisy as other hair dryers.