Acoustic trauma
Acoustic trauma is damage to hearing caused by exposure to loud noise. The noise may have been brief, such as an explosion, or continuous, such as factory noise. It results in hearing ability that is normal for low frequency sounds but considerably reduced for high frequencies.

A typical audiogram for steeply sloping hearing losses, where hearing is normal through 1000 Hz and then falls steeply.

The hearing loss resulting from acoustic trauma is typically sensorineural. Hearing is often normal through frequencies of around 1000 Hz, but damaged hair cells in the cochlea cause an inability to perceive high frequency sounds, with the greatest degree of hearing loss typically seen at around 4000 Hz. This is also referred to as a steeply sloping hearing loss. People with noise induced hearing loss often have a reduced tolerance to loud sound in the high frequency range and may experience ringing or buzzing sounds, known as tinnitus, in one or both ears.

As mentioned, the cause of the hearing loss can be long-term exposure to loud noise (for example, concerts or noisy workplaces), or can be the result of a brief, very loud sound (such as an explosion or a gunshot). This reduction in hearing is often temporary, but in case of repeated exposure to such sounds the reduction may become permanent. Generally it can be said that the louder the noise is, the more quickly the noise may cause damage to the function of the ear.

Protection against noise exposure
Ear protection can offer some defense against acoustic trauma and its related hearing loss.  It is important to avoid excessively loud noise whether work or socially related.  Check with your employer regarding any existing safety recommendations for ear protection in the workplace.  Be sure to “turn down the sound”: don’t self-induce hearing loss with exposure to excessively loud music.  Wear ear protection during recreational activities that may involve high level sound, e.g. snowboarding.