Temporary reduction of hearing sensitivity as indicated by the increase of hearing threshold level occurs after exposure to loud sounds. This can become permanent if the exposure is prolonged. The louder the sound, the shorter the exposure time to produce permanent impairment. Damage is greater if the sound contains impulsive components caused by percussive elements in the source.
When your hearing is damaged by loud sounds, it is the hair cells in the 18th set, bark 18, which are damaged. This is irrespective of the nature of the sound causing the damage. As damage increases with further exposure, the next bark down is destroyed and the missing frequency band broadens, reaching in some cases down to 1kHz. At that point, understanding speech will be almost impossible.