Explanation:
1. The types of audio equipment are generally classified as "outgoing sound" and "input sound".If the microphone is aimed at the stereo,it will produce a very harsh and shrill sound.This shrill sound is called "howling" or “feedback gain.”
2. This happens because the sound from outside the speaker goes into the mic that is being aligned, and the mic sends the sound back to the speaker, many times a second.So the sound will be infinitely amplified, and if the mic can't be taken away in time, the shrill sound will continue until the sound system breaks down.
3. The phone will be integrated with a stereo and a microphone, which means "speaker" and "microphone".Both the microphone and the speaker are used in a voice or video chat, and if the two phones are very close to each other, the noise will appear.The distance between the two phones or the end of the call can be eliminated.