Sony MDR-NC500 Headphones

I purchased the Sony MDR-NC500d noise canceling headphones about a year ago and they did have a problem with thumping on the left channel. Instead of returning them to the store where I purchased them I contacted Sony and requested a replacement. The replacement they sent me work perfectly and they sound  better than the original pair. I researched the model for issues and found out there were problems with earlier production models. Dealing with Sony was easy. This model has three noise canceling modes. When you first turn them on they automatically select the correct mode for your envoirnment or if you hold down the mode button for a few seconds it will switch to manual mode and then you can select either of the three noise canceling modes. This model has an internal lithium ion rechargeable battery that lasts about 55 hours and as well the MDR-NC500d comes with an external battery pack that you can use if the internal battery depletes in the middle of use. The external battery pack uses two AA size batteries. The noise canceling feature of these headphones works very well. The MDR-NC500d uses digital noise canceling technology apposed to analog noise canceling technology. In my opinion Digital noise canceling technology works much better. When I use analog noise canceling technology i can feel a pressure inside my ears that I just do not feel with the Digital Sony MDR-NC500d. I am a pilot and am on smaller aircraft often and have used these headphones when not in control of the plane and the noise canceling feature in mode three works better than my aviation headset which cost ten times the cost of the MDR-NC500d. I use the MDR-NC500d headphones with my Ipod and my HTC touch pro 2 and the audio reproduction is really top notch. The high frequency reproduction is very crisp and the low frequency reproduction is very deep. As well they are very comfortable to wear for long trips. They come with a large carrying case that holds the headphones and all of the accessories and have standoffs for the ear cups so the ear cushions do not get flat when stored. The carrying case is a bit large for me but it can house your Ipod or other device as well. The MDR-NC500d headphones are a bit pricey but you get what you pay for. The Sony MDR-NC500d noise canceling headphones are definitely top of the line!