The purpose of the small round hole at the bottom of the phone:

In fact, the small round hole at the bottom of your phone is a secondary microphone, playing a crucial role in the dual microphone system that helps reduce noise. This noise-canceling microphone is integrated into most modern smartphones. Thanks to this microphone, your calls will be clearer and of higher quality. Without it, your voice wouldn’t be transmitted clearly to the listener.Thanks to this small hole, even in noisy environments, you can still hear and transmit your voice clearly. Placing the microphone at the bottom of the phone near your mouth helps capture and transmit your voice better, enhancing call quality.

Sound waves pass through this microphone and are amplified, allowing the listener on the other end to receive clearer audio. Without the secondary microphone, call quality would significantly decrease.

Today, most mobile phones have two noise-reducing microphones, one at the top and one at the bottom. When the phone is affected by environmental noise, the secondary microphone reduces this noise, leaving only the call’s audio. This technology, known as “dual microphone noise reduction,” makes calls clearer even in noisy environments.