WHO - Safe Sound Levels
Guideline for Community Noise
To protect the residents from Noise in the urban areas
To protect the majority of people from being seriously annoyed during the daytime, the outdoor sound level from steady, continuous noise should not exceed 55 dB LAeq on balconies, terraces and in outdoor living areas. To protect the majority of people from being moderately annoyed during the daytime, the outdoor sound level should not exceed 50 dB LAeq. Where it is practical and feasible, the lower outdoor sound level should be considered the maximum desirable sound level for new development
To protect the majority of people from being seriously annoyed during the daytime, the outdoor sound level from steady, continuous noise should not exceed 55 dB(A), few are moderately annoyed at LAeq levels below 50 dB(A). Outdoor sound levels during the evening and night should be 5-10 dB lower than during the day.
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https://www.who.int/europe/publications/i/item/WHO-EURO-2018-3287-43046-60243
Road traffic noise
GDG recommendations.
For average noise exposure, it is strongly recommended that the noise levels produced by road traffic will be reduced below 53 decibels (dB) Lden, as road traffic noise above this level is associated with adverse health effects
For night noise exposure, it is recommended reducing that the noise levels produced by road traffic be reduced below 45 dB Lnight, as night-time road traffic noise above this level is associated with adverse effects on sleep.
To reduce health effects, it is strongly recommended that policy-makers implement suitable measures to reduce noise exposure from road traffic in the population exposed to levels above the guideline values for average and night noise exposure. For specific interventions, the GDG recommends reducing noise both at the source and on the route between the source and the affected population by changes in infrastructure
Aircraft Noise
GDG recommendations
For average noise exposure, the GDG strongly recommends reducing noise levels produced by aircraft below 45 dB Lden., as aircraft noise above this level is associated with adverse health effects
For night noise exposure, the GDG strongly recommends reducing noise levels produced by aircraft during night time below 40 dB Lnight., as night-time aircraft noise above this level is associated with adverse effects on sleep.
To reduce health effects, the GDG strongly recommends that policy-makers implement suitable measures to reduce noise exposure from aircraft in the population exposed to levels above the guideline values for average and night noise exposure. For specific interventions the GDG recommends implementing suitable changes in infrastructure.