From Wikipedia, the free encyclopediaAuditory 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.[1] These are distinguished from each other by several characteristics listed individually below.Short-term fatiguefull recovery from TTS can be achieved in approximately two minutesthe TTS is relatively independent of exposure duration[1][2]TTS is maximal at the exposure frequency of the soundLong-term fatiguerecovery requires a minimum of several minutes but can take up to several daysdependent on exposure duration and noise level[1][2]Contents [hide] 1 Physiology1.1 Affected anatomy1.2 Affected mechanisms1.2.1 Traveling wave theory1.2.1.1 Classical passive system1.2.1.2 Active process1.2.2 Excessive vibrations1.2.3 Recovery1.3 Protective measures1.3.1 Toughening and energy spread1.3.2 Substances1.3.2.1 Furosemide1.3.2.2 Salicylic Acid1.3.2.3 Antioxidants1.3.2.4 Limitations2 Risk increasing factors3 Experimental Studies3.1 Human3.2 Marine mammals3.2.1 Dolphin3.2.2 Harbour porpoise3.2.3 Harbour seal3.3 Rodents3.3.1 Mice3.3.2 Rats3.3.3 Guinea-pigs3.3.4 Chinchillas3.4 Fish4 ReferencesPhysiology[edit]Affected anatomy[edit]Diagram of the Human Ear AnatomyNote: The complete anatomy of the ear is extensive, and can be divided into theinner ear and outer ear.The remainder of this article mainly references the cochlea, outer hair cells, andOrgan of Corti.In general, structural damages to any anatomical part of the ear can cause hearing-related problems. Usually, minor bending of the stereocilia (inner ear) is associated with temporary hearing loss and is involved in auditory fatigue. Complete loss of the stereocilia causes permanent hearing damage and is more associated with noise-induced hearing loss and other auditory diseases.The outer hair cells, or OHCs, can be thought of as microamplifiers that provide stimulation to the inner hair cells. The OHCs are the most fragile of the hair cells, hence their involvement in auditory fatigue and other hearing impairments.Additional Images for Location of Anatomical PartsDepiction of inner ear showing CochleaDepiction of Cochlea showing Organ of CortiOrgan of Corti showing hair cellsAffected mechanisms[edit]Traveling wave theory[edit]Temporary threshold shifts related to auditory fatigue are related to the amplitude of a stimulus-driven traveling wave.[3] This is believed to be true because the vibration propagated by the active process is not usually at the center of the maximum amplitude of this wave. Instead, it is located much further down and the differences associated between them explain the shift in threshold.[1] The TTS that is experienced is the exhaustion of the active system located at the locus of the traveling wave driven by the cochlear amplifier described below.[3] Auditory fatigue can be explained by the relative activity of the active process at low-level stimulation (<30dB).[1]Classical passive system[edit]There are two different systems associated with the mechanics of the cochlea: the classical passive system and an active process. The passive system works to stimulate the inner hair cells directly and works at levels above 40dB.[3] At stimulation levels that prevent the excitation of the passive system, prolonged noise exposure results in a