The noise level of plasma cutting is not only affected by the system being used, but is also dependent on the amperage, gas type and cutting table style. Other factors related to noise levels are environmental like building height, walls, and distance from operators. Walls and other obstacles tend to reflect noise and of course the further away from sound the lower the decibel level will be.
Most regulations put the acceptable noise level exposure at 85 dBA in an 8-hour period.
“OSHA's permissible exposure limit (PEL) is 90 dBA for all workers for an 8-hour day. The OSHA standard uses a 5 dBA exchange rate. ... the National Institute for Occupational Safety and Health or NIOSH, which is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness, would recommend limiting the 8-hour exposure to less than 85 dBA. At 100 dBA, NIOSH recommends less than 15 minutes of exposure per day.”
So, how loud is 85 dBA?
85 dBA is about as loud as a gas-powered lawnmower or a noisy restaurant, to put that into perspective the inside of a car at 60 mph is about 70 dBA and a vacuum cleaner is about 75 dBA. What about plasma? Well a typical plasma system, cutting on a downdraft table is going to range between 90 to as much as 120 dBA or higher, which is considerably higher than what OSHA recommends.
What are some solutions to prevent hearing damage? Obviously, the easiest solution is to wear approved hearing protection. Hearing protection should be required for the operator and anyone working near the plasma system. Another option is to use a water table instead of a downdraft table. Some older studies have indicated that noise levels can be reduced by as much as 25%. That means that if measuring a sound level of 100 dBA cutting on a downdraft table, a sound level of only 75 dBA or better, could possibly be achieved. Another possible solution involves building or placing sound barriers or sound absorbing material in strategic locations to reduce the decibel levels actually reaching the operator and those working near the table.
Whatever, solutions you decide upon, one thing to remember is that most plasma cutting can and will damage worker’s hearing. Hopefully, this article has answered some questions about the potential detrimental effects plasma cutting can cause to hearing and given you some suggestions on resolving them. OSHA has many regulations relating to this topic found under; 29 CFR 1910; additional resources available include, but are not limited to the following:
American National Standards Institute (ANSI)
S3.1, Maximum Permissible Ambient Noise Levels for Audiometric Test Rooms. Specifies maximum permissible ambient noise levels (MPANLs) allowed in audiometric test rooms.
S3.44, Determination of Occupational Noise Exposure and Estimation of Noise-Induced Hearing Impairment.
S3.6, American National Standard Specification for Audiometers. Includes specifications and tolerances for audiometers and standard reference threshold levels for audiometric transducers.
S12.6, Methods for Measuring the Real-Ear Attenuation of Hearing Protectors. Specifies laboratory-based procedures for measuring, analyzing and reporting passive noise-reducing capabilities of hearing protection devices.
S1.4, American National Standard Specification for Sound Level Meters. Establishes performance and accuracy requirements for sound level meters.
S1.25, American National Standard Specification for Personal Noise Dosimeters. Contains specifications for performance characteristics of personal noise dosimeters.
American Conference of Governmental Industrial Hygienists (ACGIH)
ACGIH has established exposure guidelines for occupational exposure to noise in their Threshold Limit Values (TLVs) (85 dBA PEL with a 3 dBA exchange rate).