An Applied Investigation Into Graphics Card Coil Whine

jones_supa writes We all are aware of various chirping and whining sounds that electronics can produce. Modern graphics cards often suffer from these kind of problems in form of coil whine. But how widespread is it really? Hardware Canucks put 50 new graphics cards side-by-side to compare them solely from the perspective of subjective acoustic disturbance. NVIDIA's reference platforms tended to be quite well behaved, just like their board partners' custom designs. The same can't be said about AMD since their reference R9 290X and R9 290 should be avoided if you're at all concerned about squealing or any other odd noise a GPU can make. However the custom Radeon-branded SKUs should usually be a safe choice. While the amount and intensity of coil whine largely seems to boil down to luck of the draw, at least most board partners are quite friendly regarding their return policies concerning it.

Comments

The Cause

[labnet]

I've designed lots of these little switch mode supplies. (SMPSs)
The noise comes from the inductors. Inductors are coils of wire around a ferrite. When the current changes through the wire, the wire physically expands and contacts from every other wire. This is the source of the noise. (SMPSs normally switch from 200kHz to 2MHz, so well outside our audio range)
There are a few things a designer can do.
1. Encapsulate the coil. This holds the wire tighter together and can minimise noise, but is only usually used in large inductors like those in invertors for UPSs or solar.
2. Eliminate subsonic oscillation with good multi-pole compensation. Switch mode power supplies have, have first second and third order responses which require filters to damp them. If you don't design these filters well, you can get subsonic oscillation which falls into the audio band. The power supply still regulates OK, but you can get that annoying whine.
3. Occasionally the noise can also come from a periodic load with that falls into an audio range. More capacitors on the output can help that.

Also, very very occasionally, it can come from ceramic capacitors that use a high k dielectric that are microphonic, but in my experience it is usually the capacitor acting as a microphone that upsets the circuit.

Re:The Cause

[Charliemopps]

Have you ever noticed if this effect gets better depending on the shape? I use transformers in audio amps I build, and often there's a marked difference if I use R-core over EI or Toroid. But this is signal noise and not physical noise. If the transformer is making physical noise, I'd never be able to hear it over my guitar solo :-p

Re: The Cause

[CODiNE]

Slashdot no longer the place you used to go?
While it's a bit more mainstream audience than back in the day... you still get great comments like this one from time to time.

So when you think Slashdot is dead, remember this post.

Re:The Cause

[labnet]

AC is correct. Most forms of subharmonic oscillation are caused by slope compensation issues, but pole filtering can also be an issue . For those who want the nitty gritty details, see this. http://www.ti.com/lit/ml/slup2...

Re:The Cause

[PPH]

When the current changes through the wire, the wire physically expands and contacts from every other wire.

Not just the wires. But the core physically changes shape due to magnetostriction. The only was to reduce this is by careful selection of the inductor magnetic material and/or reducing the flux density in the core.

Re: The Cause

[plcurechax]

BTW, it would be kind of awesome if the computer hardware testing sites incorporated sound tests into their general testing of stuff.

You mean like this:
  Tom's Hardware: Sapphire's Vapor-X R9 290X 8GB - Temperature, Noise And Power.

Actually I continuously get frustrated by "enthusiast" computer sites reviews who seems to being entirely lacking in technical knowledge when it comes to anything beyond quoting the manufacturers press material. Half of them might as well have a companion site reviewing shoes and fashion tends given their display of technical ignorance.

Re:The Cause

[Anonymous Coward]

Full disclosure: I worked on this *exact* issue at NVIDIA for a brief period, although several generations ago. Usual disclosure applies - the below is my opinion, not theirs.

It doesn't surprise me that the NVIDIA reference cards do pretty well; they took the issue as seriously as some of their customers do. We made some fancy measurements to evaluate different methods of reducing the noise; indeed, some of the "common sense" things a designer can do are actually wrong. For example, #1 from the parent (fill the inductor package with something to keep the coil from moving) isn't necessarily a good idea. In some cases, that actually makes the vibration *worse*; rather than prevent the coil from moving, it helps transmit the motion of the coil to the PCB, which can then act like a sound board, making the tiny coil's vibration into something audible. (The sound board is the part of a musical instrument that is forced by the string to vibrate, making sound. It's what makes an acoustic guitar make noise when a string is plucked, while an electric guitar is relatively silent with no amp.)

That's not to say that encapsulation is a bad idea necessarily - just that this is a much more difficult problem to solve than you might imagine at first glance. And something that works well for a particular application/GPU/inductor/card combination might not work as well for a different combination.

A long time ago, I had a PowerBook G4 that had a buzzy whining that I later (while working on this problem) learned was from the inductors. I discovered that by using the CHUD Tools part of Apple's developer tools to disable the "Nap" option (this is the CPU Nap power-saving mode, not the much more recent "Power Nap" marketing-branded feature), the whining would go away, because the current in the inductors was much closer to constant.

Re:My nvidia card started whining after lightning

[adolf]

I used to have a Sound Blaster Pro which had some lightning damage. Something on the board had turned microphonic, and you could shout at the card and hear it through the line output.

Fun stuff.

Anybody familiar with the manufacturing side?

[fuzzyfuzzyfungus]

I understand that high-frequency magnetics are at risk of physical oscillation(the detailed math is right over my head; but all it takes is one part of the part attracting or repelling another part of the part, at least under some input waveforms, and you'll potentially see movement, which easily enough turns to sound); but the seemingly obvious solution is just to pot the magnetics in an adequately thermally conductive epoxy or other encapsulant.

Does anybody know if that just adds too much cost, without performance benefit, and so gets cut during the BOM penny pinching? Do potting compounds have properties that degrade the performance or efficiency of common magnetics? Why is it that, if coil whine is an issue, they aren't just dipping the things in epoxy and calling it a day?

Re:Anybody familiar with the manufacturing side?

[slew]

I understand that high-frequency magnetics are at risk of physical oscillation(the detailed math is right over my head; but all it takes is one part of the part attracting or repelling another part of the part, at least under some input waveforms, and you'll potentially see movement, which easily enough turns to sound); but the seemingly obvious solution is just to pot the magnetics in an adequately thermally conductive epoxy or other encapsulant.

Does anybody know if that just adds too much cost, without performance benefit, and so gets cut during the BOM penny pinching? Do potting compounds have properties that degrade the performance or efficiency of common magnetics? Why is it that, if coil whine is an issue, they aren't just dipping the things in epoxy and calling it a day?

Unfortunately mechanical damping of the inductor vibration isn't as effective as simply reducing the amplitude of driving frequency in the audio bands. Remember this is a sub-harmonic that is being excited by a non-linear coupling to the audio frequency. Basically the energy in a higher frequency is being converted into a lower audible mechanical frequency.

Theoretically, simply changing the mass of the physical oscillation (e.g. cementing it to something heavier) only slightly modifies the frequency of the oscillation (potentially creating more audible noise) and it still doesn't change the energy much. Viscous damping of the mechanical frequency might help a little bit more. Unfortunately, in practice, surrounding things like solder joints in potting compounds is risky as they have a different thermal expansion coefficients and it can cause additional mechanical stress (resulting in reduced mechanical reliability).

In the end, mechanical means are still not going to be as effective as changing the circuit to reduce the amount of switching energy frequencies which are coupled to the audio frequency bands. Probably even from a total system cost point of view...

Re:Mac Pro 2013?

[fuzzyfuzzyfungus]

No idea if it's the GPU; but high-frequency magnetics are all potential culprits (as are low frequencies, though 50/60Hz is usually 'hum' rather than 'whine'), and a modern laptop is just stuffed with DC/DC converters keeping the various ICs fed, so if it isn't the GPU's support system, it's another fairly similar one.

Re:Mac Pro 2013?

[Sable Drakon]

The PCBs. Take a moment to think about it. That is naturally where all the inductors are mounted.

Like bearing noise in a full-throttle jet engine

[idontgno]

Are people actually hearing inductor acoustic oscillation over FAN NOISE? If you can hear yourself think over your graphics card, YOU'RE NOT A REAL GAMER!.

Re:To me this is good news

[Zordak]

My anecdotal experience is that sometimes it's a ceramic diode getting hammered by out-of-spec back-voltage and ready to explode, and sometimes it does explode spraying ceramic shards all over the electronics lab. Root causes may include a dodgy transformer (pulled out of an old Hammond organ) with a highly questionable output waveform because you're a broke undergrad and it was cheaper than buying a new one.