Loss of sensitivity to sounds as a result of auditory stimulation, manifesting as a temporary shift in auditory threshold. The temporary threshold shift, tts, is expressed in decibels. Auditory Fatigue is defined as a temporary loss of hearing after exposure to sound. This results in a temporary shift of the auditory threshold known as a temporary threshold shift (TTS). The damage can become permanent (permanent threshold shift, PTS) if sufficient recovery time is not allowed for before continued sound exposure. When the hearing loss is rooted from a traumatic occurrence, it may be classified as noise-induced hearing loss, or NIHL. There are two main types of auditory fatigue, short-term and long-term. These are distinguished from each other by several characteristics listed individually below. Short-term fatigue * full recovery from TTS can be achieved in approximately two minutes * the TTS is relatively independent of exposure duration * TTS is maximal at the exposure frequency of the sound Long-term fatigue * recovery requires a minimum of several minutes but can take up to several days * dependent on exposure duration and noise level. An OSH glossary used in safety and health at work which is, adopted by ILO