The problem obviously stems from the fact that these applications use only the upper cell phone microphone, which should be used only for noise canceling. Obviously, this issue is also revealed in older models, including the OnePlus 5, OnePlus 5T and OnePlus 3. Not all applications are affected; Instagram, for one, does not seem to have this audio problem when playing a sound recorded by OnePlus.
Some users of OnePlus 6 and OnePlus 6T are wondering if the problem with the microphone is why they have trouble launching Google Assistant when "Hey Google" appears. Fixing this problem may require nothing more than updating the software, although it includes third-party applications.