Noise Study » Noise Limit

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Noise Limit

Environmental sound study has to be performed for environmental place and industrial plant with consideration of noise criteria. INERTANCE has studies the related sound criteria such as work area noise, restricted noise area, absolute noise limit, indoor noise assessment (NC curve sound limit) for speech and work interference, etc. The definition of noise standard is generally required for following reasons;

  • To reduce speech and work interference
  • To ensure the warning signals are audible
  • To conserve the hearing of workers
  • To allow adequate speech, telephone, and radio communication
  • To maintain working efficiency
  • To provide the quite accommodation
  • To prevent annoyance to the neighboring community
  • Noise limit application as per OSHA (Occupational Safety and Health Administrator), etc.
Environmental sound measurement
Environmental sound measurement

Sound limit – Work Area Noise

Sound pressure level including existing background noise in the work area within plant work area shall not exceed normally 85 ~ 90 dB(A) at any point 1 meter away from any equipment surface. This specific noise limit has to be followed from project requirements.

Noise criteria – Restricted Noise Area

Restricted areas are those work areas in the plant where it is not reasonably practicable to reduce the noise level below the work area limit. Such a restricted area limit may be between 85 dB(A) and 115 dB(A). Permanent warning signs to indicate the mandatory use of ear protectors shall be installed at boundaries of restricted area.

Noise limit, Noise criteria
Noise limit, Noise criteria

Sound Criteria – Absolute Noise Limit

The sound pressure level shall not normally exceed 115 dB(A) at any time and at any location which is accessible to workers in any situation, including emergency such as the blowing of safety relief valves. This specific noise criteria has to be followed from project requirements.

Sound limit, Sound criteria map
Sound limit, Sound criteria map

Speech and work interference (Indoor noise)

The desired noise criteria curves for various indoor areas shall be applied to minimize the speech and work interference. This criteria is normally defined by NC curve criteria.

NC Curve (Noise criteria curve)
NC Curve (Noise criteria curve)

Environmental Sound

Community Noise standards shall be checked for adequate accommodation area from many kinds of noise sources. Residential noise limits are normally distinguished as Day, Evening, Night time zone respectively.

INERTANCE has a capability regarding noise and vibration engineering, and our experts are familiar with assessment of industrial noise. For further information, contact us at (

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