Slashdot Mirror
iPhone 7 Plus Makes Hissing Sound Under Load, Some Users Complain (businessinsider.com)
Several commendable users are complaining that their iPhone 7 Plus handsets are making a "hissing" noise especially when they do some heavy weight work. Some users note that this issue extends to the iPhone 7 as well. BusinessInsider reports:Stephen Hackett, cofounder of podcast network Relay FM, tweeted that his iPhone 7 Plus "makes terrible noises when under load," and shared an audio clip of the noise. TechCrunch writer (and former Apple employee) Darrell Etherington responded that his "brand new, just-unboxed [device is] doing the same thing right now." It sounds like the problem isn't affecting all devices, and it's not immediately clear what's behind it. Hackett said on Twitter that Apple will be replacing his device with a new one, which suggests it's a defect rather than just an unexpected quirk of the new smartphone's design. There's some speculation out there as to what's causing it - but nothing concrete yet. Engadget's Jon Fingas suggests it could be "coil whine," a process where electronics make an unintended noise while working, for example.
I have noticed this in most equiptment over the past 30+ years of computing. I remember hearing the processing noise from my old Amstrad PC-1512C 8086. Which didn't have any cooling fans so when I did heavy processing it would make a whining sound.
I also hear a whining sound from my wireless router, I can often hear noise on LCD Displays, especially on a full screen refresh. I expect the the iPhone 7 it is doing so much stuff (whether it being useful or not is open for a another internet flame post) and the new CPU allows it to do more enough to cause a noise.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.
Given that Apple is apparently quite obscessed with making their device the same thickness as a sheet of onion skin paper, the issue is likely a combination of things.
Namely, thermal noise needs to be overcome with higher voltages, which then get switched at pretty high speeds. That switching of higher than normal voltages (because it is under load, and having to overcome passive cooling only) coupled with a most likely saturating floating ground, means RF signal leakage. Given that one of the proposed reasons for Apple's removal of the headphone jack was that they were having problems with RF noise being produced and picked up on the headphones (and nothing to do with "Courage") I find this likely, and suspect the issue to be more systemic than apple wants to admit, especially in light of the Samsung battery disaster.
(EG, the reality that you can't reasonably push a design that thin without having very real problems with the electronics does not fly well with the ivory tower designers with sticks up their asses at Apple, but their marketing droids pay better attention, and realize this is a potential problem they need to be mum about. I would expect higher rates of failure from out of expected tolerance voltages on devices driven hard, and apple blaming the users, rather than the hardware like they should be.)
The big change in DCDC design is in the different modes of operation that a DCDC controller can support. It used to be simple pulse width modulation but now we have pulse width modulation and, to use a term adopted by Linear, "Burst" mode DCDC converters. The purpose of the "burst" mode is to achieve low power level efficiency by on/off modulating the DCDC converter. The resulting on/off modulation can be within the acoustic range even if the actual DCDC converter is switching in the MHz range. So Linear, TI, Analog - they all now support their own version of a "burst" mode.
In the past 5 years, far more parts from various manufacturers are available for designing systems that goes to sleep but require always-on power rails. You used to have to pair a DCDC and LDO together to achieve the best of both worlds. And companies like Murata have capacitors specifically designed to assist in alleviating the whine. Check out their product line for a more detained description. I have designed and built power supplies that have had a noticeable whine - typically under low load. So I can confirm - it is the caps.