By default, iPhones use noise cancellation to reduce ambient noise in phone calls made through the Phone app. While noise cancellation is ideal for most calls, some find it disorienting. If you believe the same, it is easy to turn it off completely. See how.
What is noise cancellation?
The noise cancellation on the phone, first introduced in iOS 7, monitors flat of ambient noise and produces an inverse sound signal to cancel this background noise, so you do not hear it on the phone call. THE technology works best with continuous low noise level. But sometimes it can produce a terribly quiet phone conversation or deal with the unpredictable Sounds, such as small noises from the crowd or a low background music.
Also, some people find the noise canceling effect uncomfortable (similar to problems with headphones isolating noise), especially when using headphones. Fortunately, noise cancellation is easy to turn off on iPhone - just by going to Settings.
How to turn off noise cancellation on iPhone
First, open "Settings" on your iPhone.
In Settings, go to the "Accessibility" section.
Scroll down to the Hearing section and press “Audio / Visual”.
Press the "Phone Noise Cancellation" switch to turn it off.