Table 3-1. Typical A-Weighted Noise Levels Noise Level Common Outdoor Activities Common Indoor Activities (dBA) 110 Rock band — — Jet fly-over at 1000 feet 100 — — Gas lawn mower at 3 feet 90 — — Diesel truck at 50 feet at 50 mph Food blender at 3 feet 80 Garbage disposal at 3 feet — — Noisy urban area, daytime Gas lawn mower, 100 feet 70 Vacuum cleaner at 10 feet — — Commercial area Normal speech at 3 feet Heavy traffic at 300 feet 60 — — Large business office Quiet urban daytime 50 Dishwasher next room — — Quiet urban nighttime Theater, large conference room (background) 40 — — Quiet suburban nighttime 30 Library — — rural nighttime Bedroom at night, concert hall (background) 20 — — Broadcast/recording studio 10 — — Lowest threshold of hearing 0 Lowest threshold of human hearing — — Source: Caltrans 2013. Human Response to Changes in Noise Levels As discussed above, doubling sound energy results in a 3-dB increase in sound. However, given a sound level change measured with precise instrumentation, the subjective human perception of a doubling of loudness will usually be different than what is measured. Under controlled conditions in an acoustical laboratory, the trained, healthy human ear is able to discern 1-dB changes in sound levels, when exposed to steady, single-frequency (“pure-tone”) signals in the midfrequency (1,000 Hz–8,000 Hz) range. In typical noisy environments, changes in noise of 1 to 2 dB are generally not perceptible. However, it is widely accepted that people are able to begin to detect sound level increases of 3 dB in typical noisy environments. Further, a 5-dB increase is generally perceived as a distinctly noticeable increase, and a 10-dB increase is generally perceived as a doubling of loudness. Therefore, a doubling of sound energy (e.g., doubling the volume of traffic on a highway) that would result in a 3-dB increase in sound, would generally be perceived as barely detectable.
Table 3-1. Typical A-Weighted Noise Levels Common Outdoor Activities Noise Level (dBA) Common Indoor Activities — 110 — Rock band Jet fly-over at 1000 feet — 100 — Gas lawn mower at 3 feet — 90 — Diesel truck at 50 feet at 50 mph Food blender at 3 feet — 80 — Garbage disposal at 3 feet Noisy urban area, daytime Gas lawn mower, 100 feet — 70 — Vacuum cleaner at 10 feet Commercial area Normal speech at 3 feet Heavy traffic at 300 feet — 60 — Large business office Quiet urban daytime — 50 — Dishwasher next room Quiet urban nighttime — 40 — Theater, large conference room (background) Quiet suburban nighttime — 30 — Library rural nighttime Bedroom at night, concert hall (background) — 20 — Broadcast/recording studio — 10 — Lowest threshold of hearing — 0 — Lowest threshold of human hearing Source: Caltrans 2013. Human Response to Changes in Noise Levels As discussed above, doubling sound energy results in a 3-dB increase in sound. However, given a sound level change measured with precise instrumentation, the subjective human perception of a doubling of loudness will usually be different than what is measured. Under controlled conditions in an acoustical laboratory, the trained, healthy human ear is able to discern 1-dB changes in sound levels, when exposed to steady, single-frequency (“pure-tone”) signals in the midfrequency (1,000 Hz–8,000 Hz) range. In typical noisy environments, changes in noise of 1 to 2 dB are generally not perceptible. However, it is widely accepted that people are able to begin to detect sound level increases of 3 dB in typical noisy environments. Further, a 5-dB increase is generally perceived as a distinctly noticeable increase, and a 10-dB increase is generally perceived as a doubling of loudness. Therefore, a doubling of sound energy (e.g., doubling the volume of traffic on a highway) that would result in a 3-dB increase in sound, would generally be perceived as barely detectable.
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