Yesterday, we reported that some iPhone 7 handsets have hissing sounds emanating from the back especially when the processor is under heavy load. There are also complaints that there is a loss of cellular service after switching the phone back from Airplane Mode.
1. Hissing under load
The first issue reported was a strange hissing sound originating from the back of some iPhones, especially when under heavy processing load.
Stephen Hackett of Relay FM tweeted the issue on Saturday stating that his iPhone 7 "makes terrible noises when under load."
According to the MacRumors forums, other iPhone 7 owners are confirming the hissing-under-load issue and were advised by AppleCare to bring the affected handsets to their respective Apple Store for replacement. The problem is that some of the iPhone 7 replacement handsets are exhibiting the same hissing issue.
It's unclear at this point if the noise is a general issue of all iPhone 7 models or if it is just a problem with defective batches.
The general theory is that this could be "coil noise," the sound an electronic part normally makes especially if it's not properly dampened. Although the phenomenon is commonly associated with desktop computer components, the iPhone 7's A10 processor is powerful enough to elicit worse coil noise than previous models.