The real problem with the iPhone 7 and iPhone 7 Plus could actually be the new A10 processor and not the absence of the universal headphone jack. Apparently, following the release of Apple’s new smartphones, some owners are complaining that their new iPhones are producing a “hissing” sound when they are being used heavily.

Apple Insider has learned recently that some iPhone 7 and iPhone 7 Plus owners are complaining about an audible sound coming from within their smartphones and not from the speaker system. Users have reportedly voiced out their concern over the alarming “hissing” sound on social media.

One of the owners of the defective units is Relay FM co-founder Stephen Hackett who was among the first to voice out this issue on Twitter. He wrote, “My iPhone 7 Plus makes terrible noises when under load.” He also provided a clip exposing the disturbing sound of his device alongside his tweet.

Since sharing his observation on the social networking site, many gave their two cents on what could be causing the noise. Recruitment consultant Chris Smith opined that it could be the Taptic Engine, while biochemical engineer Kris Janssen remarked that the sound is normal for CPUs and backed his statement with a link to a SuperUser thread on processor noise.

Meanwhile, Hackett revealed in his updates that he contacted Apple’s warranty and technical support department AppleCare, and he was directed to got to an Apple Store to have it replaced. Unfortunately for him, since there are no stocks of the iPhone 7 Plus in stores, he would have to wait 5.-7 business days to have his defective handset replaced. 

AppleInsider notes that it is still not clear whether this issue is really due to the A10 processor, but Apple should be willing to offer free replacements for first batch iPhones with a defective component. 

While the hissing sound is alarming, Engadget says that it is still worth mentioning that the devices still function well. However, the tech site maintains that smartphones are supposed to be silent and having this “hissing” sound is just disconcerting. 

Apple has yet to comment on the complaints against its iPhone 7 and iPhone 7 Plus handsets that officially hit stores just this Friday after debuting publicly on Sept. 7.