Four-month-old baby voice, may be related to loud crying, acute laryngitis or laryngeal trauma, etc., according to the severity of the condition can cause different degrees of damage and danger to the child, such as acute laryngitis may cause respiratory difficulties. 1. loud crying: four months baby long time shouting or loud crying, can cause the mucous membrane of the vocal folds temporary excessive application of congestion, cause voice rough, hoarse, but generally after soothing, rest, hoarseness can be gradually relieved. 2. Acute laryngitis: baby in the occurrence of colds, there can be a viral invasion, when the infection gradually downward expansion, resulting in laryngeal mucosa acute katastrophic inflammation, hoarseness, coughing or laryngeal pain and other manifestations of the disease can be life-threatening, resulting in respiratory distress, measures should be taken immediately to relieve the discomfort of the child. 3. Laryngotracheal stenosis: can be caused by congenital diseases, such as laryngeal chondrodysplasia, laryngeal chondromalacia, etc., due to the emergence of vocal stenosis, can be manifested as hoarseness, which can cause respiratory distress in children, should be treated promptly. The baby’s voice is mute, we should pay attention to timely to the hospital specialist consultation, clear cause of hoarseness, if necessary, tracheotomy, active on the cause of symptomatic treatment.