If your thinking of a pair of noise cancelling headphones for less that £50. Get these! the quality of the music through them is brilliant; these headphones are powered so the power input acts as an amplifier as also a noise cancelling system, therefore producing very clear sound. the noise cancelling being near 90% makes these a bargain compared to others on the market.
I bought these as a pair of headphones to use whilst playing the drums. I strongly recommend these for drummers as not all the external noise is cancelled. I can clearly hear the drums with these without turning up the volume above a normal level.
Oh and this is the best place to get these, best price by far