Minecraft monster sounds without monsters?

I usually play creative and I'm relatively new to the survival world. I looked on the internet but found nothing. I hear zombie and spider noises near my base. I have a cave near my base, but it ends in two dead ends and is completely illuminated. I also have a lake next to me, suspected drowned people, but there aren't any. The noises also come during the day and are very loud, as if the monster was standing in my immediate vicinity. I'm very scared and even that scares me at times. It's also very annoying.

Have you ever peeked under your base?

The cave in which I have already illuminated runs under my base. I don't think there's another smaller one right next to it