Noise in Call Microphone

I have bought an iPhone 11 1 week ago, I put a screen protector and I have a phone case because I don't want to scratch it or break. Yesterday, I was interested in how it sounds when I record some Voice. I get into the Voice Memos app and realized that there are some noises in the background of my recording. I'm scared about that because it's a new phone and, I really didn't drop it or hit somewhere. Also, I can hear the same noise in the WhatsApp voice message and Snapchat video. I tried to record a video on the camera app but the sound is perfect there. I think it uses another microphone, the upper one. I think I recorded the same voice before, like the day after, but the sound was completely normal. I tried to restart the phone, tried to take off my protective case... Nothing different. And something else I noticed was when I record the memo, at the beginning of the recording I can hear like a small hit, I don't know. My software version was 14.3, I have updated it to 14.4 2-3 days after the purchase.