docs(content): update background sound preference

Author: lzwjava

original/2024-12-24-background-sound-en.md

@@ -20,3 +20,6 @@ title: Prefer to Have Background Sound
 
 * It's like being in a classroom—while you focus on the board, there are background sounds from the teacher and other students. The effectiveness of your learning depends on your engagement.
 
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+Update: In the summer of 2025, I stopped preferring to have background sound. Silence may allow the mind to be peaceful.