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Decibels (dB) are a logarithmic unit used to measure sound intensity, which corresponds to perceived loudness. The scale is used to represent a wide range of sounds, from the low end of human hearing, such as a whisper or rustling leaves, to extremely loud noises like a jet plane taking off, which is near the threshold for pain at approximately 130 dB.

Decibels (dB) as a Measure of Sound Intensity

A significant portion of hearing loss, approximately one-third, is attributable to noise exposure. The risk of damage is a function of both sound intensity and exposure duration; the louder the sound, the less time is needed to cause harm. For example, listening to music through earbuds at a high volume of 100–105 decibels can lead to noise-induced hearing loss in just 15 minutes and also increases the long-term risk of age-related hearing loss.

Noise-Induced Hearing Loss

The decibel (dB) scale illustrates the intensity of everyday sounds, starting from the human hearing threshold at 0 dB. Quieter sounds include rustling leaves (20 dB), a whisper (30 dB), soft music (40 dB), and a refrigerator (45 dB). A normal conversation registers at about 60 dB. Louder sounds that can pose a risk to hearing include heavy city traffic (85 dB), a motorcycle (95 dB), and earbuds at maximum volume (105 dB). Extremely loud sounds include a music concert (120 dB), jets (130 dB), and firearms, which can reach 150 dB.

Examples of Common Sounds and Their Decibel Levels

The illustrated decibel scale connects higher sound intensity with hearing-risk labels and shorter exposure times for permanent damage. Heavy city traffic at 85 dB is labeled as causing permanent damage after 8 hours of exposure, a motorcycle at 95 dB after 6 hours, and earbuds at maximum volume at 105 dB after 15 minutes. The scale also marks 110 dB as a risk for hearing loss, 130 dB as the pain threshold, 140 dB as harmful, and firearms at 150 dB as capable of immediate permanent damage.

Hearing Damage Thresholds Based on Decibel Level and Exposure Time

An audio engineer at a concert increases the sound level from 70 dB to 90 dB. Which statement best analyzes the change in the sound's physical intensity and how it is perceived by the audience?

A sound increases in intensity from 30 dB to 50 dB. A second, much louder sound increases from 90 dB to 110 dB. How does the perceived change in loudness for the first sound compare to the perceived change for the second sound?

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