Turtle Beach has quite a reputation among gamers for being the go-to guy when it comes to headsets. They aren't cheap, but for serious game fanatics, the payout is usually worth it.\u00a0With Call of Duty: Black Ops II now hitting the shelves, Turtle Beach has released a series of limited-edition headphones to go along with the game. Pocket-lint has been playing through the new game with the top-of-the-line Ear Force Sierras plonked on our heads. So how do they sound?The Sierra headphones are designed for tournament gamers, those who need to be able to get the most from their headphones when they play online. As such, they aren't wireless, because of the interference caused by multiple wireless headsets at a gaming event. There is, however, the Ear Force Tango model, which is a touch more expensive at \u00a3299, and comes with a wireless unit.The Sierra comes in at \u00a3279, which is quite an asking price for a wired gaming headset, but it doesn't disappoint. In terms of build, you get a Black Ops II emblazoned set of earphones, with a matching orange and black wrapped lead.Inside the 'phones is a printed Turtle Beach logo, with the top cushion that rests on your head also wrapped in orange and black. They aren't exactly restrained, but definitely suit the gamer and Call of Duty style.Attached to the headphones is a large volume controller with eight different sound preset buttons that you can either customise to make your own or opt for the specially designed Treyarch offerings. These are designed to either enhance certain elements of the single-player campaign, or give you the edge in multiplayer by doing things such as raise bullet and footstep sounds.The headphones really come into their own when you realise just how customisable that Dolby Surround is. You can, for example, select the angle of each speaker, to adjust the 3D effect. It is also possible to adjust the volume of individual speaker groups in the virtual 5.1 setup. All of this is done via the simple to use LED backlit touch-sensitive volume controller.The microphone on the Sierra headset can morph your voice in order to disguise it while you are playing multiplayer, a handy feature should you like to annoy people regularly online.\u00a0In practice, we spent a long time fiddling with the sound settings to try to make our own favourites, but soon discovered the Treyarch offerings were vastly better. It is also possible to download and install on to the headphones other settings for other flagship games - Assassin's Creed III, for example.The headphones were capable of an impressively bass-heavy sound and were very detailed with a highly convincing 3D effect. There are other headphones that cost the same which might sound better with music, but these are designed specifically for surround sound games. As such, you get a vastly enhanced Call of Duty experience. It does depend somewhat on the quality of the game soundtrack, Forza Horizon, for example, sounded amazing.Voice chat was also clear and crisp and of the standard you would expect from a Turtle Beach headset.\u00a0They might cost, but these top-of-the-line Sierra headphones are seriously persuasive for a Call of Duty fan. There are cheaper options, such as the \u00a389 Ear Force Kilo, which we haven't heard yet. These come without the customisation, but are said to provide similar bass performance, although we can't be sure.