Nine-year-old children’s voices are mute and not as loud as before, which may be caused by physiological factors such as excessive use of voice, environmental dryness, or by laryngitis, vocal polyps and other diseases. 1. Physiological factors: if excessive voice, dry environment, long-term inhalation of irritating gases, may lead to children’s throat discomfort, hoarse voice, and not as loud as before. If there is no other discomfort, it is a normal phenomenon. 2. Laryngitis: Laryngitis may be caused by infection, trauma, chronic inflammation of the nasal cavity or throat. The child will have hoarse voice, throat discomfort, cough and other symptoms, manifested as a mute voice is not as loud as before. 3. Vocal polyps: Vocal polyps may be caused by improper vocalization, local inflammation and other factors. The child may appear hoarse, speak hard and not easy to make a sound. There are many reasons why a 9-year-old child’s voice is mute and not as loud as before, so parents are advised to bring their children to regular hospitals in time to undergo relevant examinations and identify the causes of the disease.