According to the National Institute for Occupational Safety and Health (2001), permanent, noise-induced hearing loss is the chief health hazard posed by occupational and recreational situations. Of the 30 million reported cases of hearing loss in the United States, one third is related to noise exposure. Noise-induced hearing loss involves the degeneration and irreparable loss of cochlear hair cells, which leads to auditory threshold deterioration. Noise can act as a mechanical stressor by overstretching inner ear tissues. If noise is too intense, it can also lead to vascular constriction, which reduces blood flow to the ear. Whether noise is harmful depends on its intensity, frequency, duration, and an individualâ€™s (genetic) susceptibility.
Noise-induced hearing loss characteristically involves high frequency (3-8 kHz) sound. These frequencies correspond to speech sounds, specifically consonants. As a result, noise-induced hearing loss can cause difficulty understanding speech, especially in the presence of background noise. Noise-induced hearing loss can occur immediately, or gradually over time, depending on the type of exposure. A condition known as temporary threshold shift (TTS) classifies transient hair cell dysfunction 24-48 hours after exposure, and is not a stable auditory threshold loss. This kind of hearing loss is the type that can occur after working with power tools or attending a rock concert. Normal hearing levels will often return after a brief, temporary period (a few hours to a few days) of experiencing a hearing loss. On the other hand, a permanent threshold shift (PTS) is irreversible, and the hearing loss is considered stable (about two weeks following exposure). This type of loss may be caused by an acoustic trauma such as a gunshot or explosion.
The world we live in can be a noisy one, and it is important to protect our ears when in harmful situations. Multiple incidences of exposure, causing temporary threshold shifts, present the possibility of adding up over time to create permanent threshold shifts. To help defend our ears from toxic noise exposure, hearing protection should be worn whenever we participate in loud activities. Different kinds of hearing protection are available to preserve our hearing. These range from single-use disposable plugs to custom ear pieces.Â Hearing protection can vary with respect to the range of attenuation levels, or stages of sound dampening. Please come visit us at Audiological Consultants of Atlanta to learn more about where and when it is appropriate to wear hearing protection, and what kind of protection fits best with your lifestyle.