Noise-induced hearing loss (NIHL) affects an estimated 5% of the worldwide population, with 30-40 million Americans exposed to hazardous sound or noise levels regularly. Sources of noise may be occupational (e.g., manufacturing, construction), blast noise (e.g., firearms or explosions), or recreational (e.g., loud music, power tools). Trauma to the inner ear can occur through transient hearing loss (temporary threshold shifts, TTS) or permanent hearing loss (permanent threshold shift, PTS). Although hearing recovers after a TTS in about 24-48 hours, growing evidence suggests that repeated TTS may lead to PTS. Both TTS and PTS lead to a decrease in hearing thresholds at 3000 to 6000 Hz.