All welding and cutting processes generate noise but some processes are much noisier than others are, such as plasma cutting and air arc gouging. Likewise some welding machines are noisier than others are and some generate noise of a higher frequency, such as pulse MIG welding.

A significant amount of work by industry has been carried out to assess noise hazard within the work place. All the data produced below is based upon work carried out by BOC in a typical work place, it can be used to indicate trends but should not be considered absolute as each work place is different.

The noise measurements were made at a distance of 1metre from the arc.

Tradesmen such as welders, platers, fitters and inspectors in busy welding shops are all likely to be exposed to noise levels above 90dB(A) as an 8hr TWA.

The type of transfer mode being used by the MIG and FCAW processes also seems to give a different level of noise produced.

There also appear to be differences in noise levels from different welding power sources, with one study reporting a range of 84-97dB for four different pulsed MIG units, measured 0.5m from the arc.

For TIG welding mild steel, stainless steel, and copper the noise levels were slightly above the background level measured in the workshop, while for aluminium TIG welding the noise levels were a somewhat higher.

Welding with high-powered lasers was found to give noise levels around 85-90dB.

As with welding the different cutting processes produce significantly differing levels of noise. The loudest of these are air-arc cutting and gouging and plasma cutting, followed by oxygen cutting with laser cutting being the quietest.

Experiments on the noise generation from plasma cutting stainless steel has demonstrated that noise emissions from 98-103dB(A) can easily be achieved when carried out in an open workshop.

With the oxygen cutting processes both pre-heating prior to cutting and cutting itself can give high levels of noise.

Although much quieter than the other two processes tests have shown that noise levels can be just below or just above the 90dB(A) level.

Tests carried out on arc-air gouging and cutting have shown the process to have very high noise levels associated with it. Values of 90-110dB have been recorded.

Grinding noise has been recorded at 103dB, at 5m from the activity, with cut-off wheels giving up to 108dB, guillotines up to 93dB and brake presses up to 87dB.

Resistance welding processes, friction welding and flash butt welding, can also give high noise levels.

The human ear is a sensitive and quite delicate organ. It can detect very small changes in sound pressure, and this detection takes place by virtue of hair cells (nerve cells) in the inner ear known as the cochlea.

Loud noise, whether continuous or impulse, can cause damage to these hair cells, and once destroyed, they do not regenerate.

Many countries have in place legislation or guideline recommendations designed to limit exposure to noise for those at work. They tend to agree that a level of 90dB(A), as a maximum 8hr time weighted average (TWA), and recognize that 85dB(A) is a safer upper limit that should be aspired to. They also seek to have risk from noise exposure and noise emissions reduced as far as reasonably practicable, requiring employees to be assessed, informed of risks, trained, and provided with suitable hearing protection, where appropriate.

Australia and New Zealand maintain a TWA of 85db with recommendations that ear protection be worn above this level and must be worn at 90db.

Most legislation requires noise levels to be reduced by engineering methods rather than by simply providing workers with ear protection. Try and reduce noise at source, or use less noisy manufacturing methods, or screen off noisy activities to protect others.

While not suitable in every case, there are some general suggestions that may be applicable to a variety of industrial situations and these include:

• Use sound absorbing materials on walls, roofs, screens to dampen sound reflection - these measures help the general work force, but not the operator of a noisy process.

• For noisy activities, like grinding, gouging, chipping, designate a specific area for these processes and acoustically screen them from other work activities.

Hearing tests (audiometry) can be carried out on those at risk, to enable any deterioration in hearing to be detected at an early stage. Audiometry involves a listener responding to electronically produced sound of various frequencies and loudness.

Noise is a fact of industrial life but it cannot always be reduced and will never be eliminated altogether. Consequently, there will always be a need for personal protective equipment (PPE) to attenuate the noise and prevent workers suffering noise-induced deafness.