Some Apple users have another item to add to the growing list of concerns with the new iPhone. According to reports from recent buyers, the iPhone 7 and 7 Plus release discernible hissing sounds when they’re under heavy stress.

Tech reviewer DetroitBORG reported a noise so faint he had to hold his phone to his ear to hear it, while blogger Stephen Hacket said the static sound could still be heard after placing the phone on a table. Regardless of the volume, most Apple customers probably don’t want their new phones to sound like a slowly-deflating kiddie pool. But as Ars Technica explains, the hissing issue may not be much of an issue at all.

Some new owners reported first hearing the noise when restoring their phones, a process that places a lot of pressure on a device’s main microchip or SoC. The iPhone 7’s SoC is located in the general area behind the Apple logo, which is the same spot many reports trace the sound back to. It’s possible then that the hissing is an example of coil noise.

Coil noise can usually be heard coming from larger electronic devices. When the moving parts of something like a high-powered processor hit a certain frequency, the whole circuit will start to vibrate and “whine.” This side-effect is more pronounced in stronger processors, which is why we’re more accustomed to hearing it from laptops and desktops than smartphones.

The iPhone’s new A10 SoC is on par with the CPUs of some recent computers, which would explain the new noise. A subtle hissing sound may just be a sign that your phone is working the way it’s supposed to. But if it’s loud enough to be distracting, that could be an indication of a poorly-dampened phone and you might qualify for a replacement.

[h/t Ars Technica]

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