Exposure to acoustic levels above what decibel level can have harmful effects?

• A. 15 dB
• B. 30 dB
• C. 50 dB
• D. 85 dB

Answer: (D)

Loud sounds become harmful to hearing when both the level and the duration of exposure are high. 85 dB is a commonly cited cutoff where the risk of noise-induced hearing loss starts to rise with typical work durations; beyond this level, prolonged exposure without protection can damage hearing. As the sound level increases, the amount of safe exposure time decreases, so exposures above this threshold require protective measures or reductions at the source. The lower levels listed are well below this risk point and are not expected to cause harm under normal steady exposure, which is why 85 dB is the best choice for indicating a level above which harmful effects can occur.