Generally while using phone accidentally the phone dropped in water. The water or dust trapped in mobile speaker and the sound is muffled. Mostly people breathe the air with their mouth to remove water or dust. By these things water went reverse into the phone. Instead, we can use speaker cleaner app. This app is available in play store. After the installation, press the start button. Immediately the air will get back through the speakers. The inside water or dust is in speakers will be clean.