A protection apparatus for a sound signal converting device, the protection apparatus protecting the sound signal converting device which has a coil and converts an audio signal supplied to the coil to a sound signal, the protection apparatus comprising: a level controller (24; 24-1; 24-2) for supplying an input audio signal to the coil in a first state with a level of the audio signal being kept, and suspending the supply of an audio signal to the coil or decreasing the level of an audio signal which is to be supplied to the coil in a second state; first temperature measurement means (21;101-106, 30; 106-108, 30) for measuring temperature of the coil as a first measured temperature; second temperature measurement means (30; 101-106, 30; 106-108, 30) for measuring temperature of the coil as a second measured temperature, independently of the first temperature measurement means; an unexpected condition controller for setting the level controller to the second state if a difference between the first measured temperature and the second measured temperature is outside a predetermined range; and a temperature controller for: keeping the level controller at the first state if the difference between the first measured temperature and the second measured temperature falls within the predetermined range with a predetermined one of the first measured temperature and the second measured temperature being lower than a first temperature, and switching the level controller to the second state if the difference between the first measured temperature and the second measured temperature falls within the predetermined range with the predetermined one of the first measured temperature and the second measured temperature being equal to or higher than the first temperature. a level controller (24; 24-1; 24-2) for supplying an input audio signal to the coil in a first state with a level of the audio signal being kept, and suspending the supply of an audio signal to the coil or decreasing the level of an audio signal which is to be supplied to the coil in a second state; first temperature measurement means (21;101-106, 30; 106-108, 30) for measuring temperature of the coil as a first measured temperature; second temperature measurement means (30; 101-106, 30; 106-108, 30) for measuring temperature of the coil as a second measured temperature, independently of the first temperature measurement means; an unexpected condition controller for setting the level controller to the second state if a difference between the first measured temperature and the second measured temperature is outside a predetermined range; and a temperature controller for: keeping the level controller at the first state if the difference between the first measured temperature and the second measured temperature falls within the predetermined range with a predetermined one of the first measured temperature and the second measured temperature being lower than a first temperature, and switching the level controller to the second state if the difference between the first measured temperature and the second measured temperature falls within the predetermined range with the predetermined one of the first measured temperature and the second measured temperature being equal to or higher than the first temperature. keeping the level controller at the first state if the difference between the first measured temperature and the second measured temperature falls within the predetermined range with a predetermined one of the first measured temperature and the second measured temperature being lower than a first temperature, and switching the level controller to the second state if the difference between the first measured temperature and the second measured temperature falls within the predetermined range with the predetermined one of the first measured temperature and the second measured temperature being equal to or higher than the first temperature.