Coil whine is the undesirable effect of electrical components creating audible noise when operating. Let's look to our friends at Wikipedia for a concise and accurate description of the phenomenon:
Coil noise is, as its name suggests, caused by electromagnetic coils. These coils, which may act as inductors or transformers, have a certain resonant frequency when coupled with the rest of the electric circuit, as well as a resonance at which it will tend to physically vibrate.
As the wire that makes up the coil passes a variable current, a small amount of electrical oscillation occurs, creating a small magnetic field. Normally this magnetic field simply works to establish the inductance of the coil. However, this magnetic field can also cause the coil itself to physically vibrate. As the coil vibrates physically, it moves through a variable magnetic field, and feeds its resonance back into the system. This can produce signal interference in the circuit and an audible hum as the coil vibrates.
Coil noise can happen, for example, when the coil is poorly secured to the circuit board, is poorly damped, or if the resonant frequency of the coil is close to the resonant frequency of the electric circuit. The effect becomes more pronounced as the signal passing through the coil increases in strength, and as it nears the resonant frequency of the coil, or as it nears the resonant frequency of the circuit. Coil noise is also noticed most often when it is in the humanly audible frequency.
Coil noise is also affected by the irregularities of the magnetic material within the coil. The flux density of the inductor is effected by these irregularities, causing small currents in the coil, contaminating the original signal. This particular subset of is sometimes referred to as magnetic fluctuation noise or the Barkhausen effect. Coil noise can also occur in conjunction with the noise produced by magnetostriction.
Gamers that frequently upgrade their graphics cards may have been witness to this problem with a particular install, or you might have been one of the lucky ones to never deal with the issue. If your computer sits under your desk, in a loud room or you only game with headphones, it's also possible that you just never noticed.
Possibly offending inductors?
The reason this comes up to today is that reports are surfacing of GeForce GTX 970 cards from various graphics card vendors exhibiting excessive coil whine or coil noise. These reports are coming in from multiple forum threads around the internet, a collection of YouTube videos of users attempting to capture the issue and even official statements from some of NVIDIA's partners. Now, just because the internet is talking about it doesn't necessarily mean it's a "big deal" relative to the number of products being sold. However, after several Twitter comments and emails requesting we look into the issue, I thought it was pertinent to start asking questions.
As far as I can tell today, GTX 970 cards from multiple vendors including EVGA, MSI and Gigabyte all have users reporting issues and claims of excessive coil noise. For my part here, I have two EVGA GTX 970 cards and an MSI GTX 970, none of which are producing sound at what I would call "excessive" levels. Everyone's opinion of excessive noise is going to vary, but as someone who sits next to a desk-high test bed and hears hundreds of cards a year, I am confident I have a good idea of what to listen for.
We are still gathering data on this potential issue, but a few of the companies mentioned above have issued official or semi-official statements on the problem.
The coil whine issue is not specific to 900 series, but can happen with any high end GPU and that MSI is looking in to ways to minimize the issue. If you still have concern regarding this issue, then please contact our RMA department.
We have been watching the early feedback on GTX 970 and inductor noise very closely, and have actively taken steps to improve this. We urge anyone who has this type of concern to contact our support so we can address it directly.
We’re aware of a small percentage of users reporting excessive “coil whine” noises and are actively looking into the issue.
We are waiting for feedback from other partners to see how they plan to respond.
Since all of the GTX 970 cards currently shipping are non-reference, custom built PCB designs, NVIDIA's input to the problem is one mostly of recommendations. NVIDIA knows that it is their name and brand being associated with any noisy GeForce cards so I would expect a lot of discussions and calls being had behind closed doors to make sure partners are addressing user concerns.
Interestingly, the GeForce GTX 970 was the one card of this Maxwell release where all of NVIDIA's partners chose to go the route of custom designs rather than adopting the NVIDIA reference design. On the GTX 980, however, you'll find a mix of both and I would wager that NVIDIA's reference boards do not exhibit any above average noise levels from coils. (I have actually tested four reference GTX 980s without coil whine coming into play.) Sometimes offering all of these companies the option to be creative and to differentiate can back-fire if the utmost care isn't taken in component selection.
Ironically the fix is simple: a little glue on those vibrating inductor coils and the problem goes away. But most of the components are sealed making the simple fix a non-starter for the end user (and I wouldn't recommend doing that anyway). It does point to a lack of leadership from board manufacturers that are willing to skimp on hardware in such a way to make this a big enough issue that I am sitting here writing about this today.
As an aside, if you hear coil whine when running a game at 500-5000 FPS, I don't think that counts as being a major problem for your gaming. I have seen a video or two running a DX9 render test at over 4500 FPS – pretty much any card built today will make noises you don't expect when hitting that kind of performance level.
As for my non-official discussions on the topics with various parties, everyone continues to reiterate that the problem is not as widespread as the some of the forum threads would have you believe. It's definitely higher than normal, and getting public acknowledgements from EVGA and MSI basically confirms that, but one person told me the complaint and RMA levels are where they were expected to be consider the "massively fast sell out rates" the GTX 970 is experiencing.
Of course, AMD isn't immune to coil whine issues either. If you remember back to the initial launch of the Radeon R9 290X and R9 290, we had similar coil whine issues and experienced those first hand on reference card designs. (You can see a video I recorded of an XFX unit back in November of 2013 here.) You can still find threads on popular forums from that time period discussing the issue and YouTube never seems to forget anything, so there's that. Of course, the fact that previous card launches might have seen issues along the same line doesn't forgive the issue in current or later card releases, but it does put things into context.
So, let's get some user feedback; I want to hear from GTX 970 owners about their experiences to help guide our direction of research going forward.