• As health and safety legislation increases employer liability, workplace noise for some remains out of sight out of mind writes Patrick O'Sullivan.

Live artillery when in the British army was an extreme noise "that goes right through your head" despite any ear protection used, says occupational physician Dr David McBride.

The New Zealand Army Reserve lieutenant-colonel and Otago University associate professor's firsthand experience is a relevant reference point for workplace noise studies, the most recent in several Hawke's Bay businesses.

He visited them a year ago, made recommendations and upon his return the region's report card reads, could do better.

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He said he was disappointed in some organisations but found Tumu Timbers innovative in finding ways to beat manufacturing noise and Bostock NZ also made progress in its pack houses.

Others were slow to make progress.

"People have had a year to do it and suddenly the year is up," he said, despite the legal onus on employers to eliminate noise.

Under health and safety laws employers have to minimise noise as a priority.

"If you can't get rid of the noise you have to minimise it by hearing protection, then you have to measure the noise routinely and you have to do everything possible to reduce the noise."

Staff needed to have their hearing tested at regular intervals to ensure ear protection was working.

Wearing ear plugs under earmuffs was necessary if extreme noise could not be eliminated at its source.

He said too much ear protection was undesirable because sensory deprivation led to feelings of isolation but noisy workplaces were unhealthy.

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Noise quickened the heart and increased blood pressure, stress hormones and fatigue. Eliminating noise correlated with increased production and healthier staff no longer unconsciously tense due to high sound levels which could cause musculoskeletal disorders.

"If you look for ways to reduce the noise you always find ways to get it down a little bit. Every little bit helps," Dr McBride said.

Ear protection needed to be checked often. Often it did not work properly because it was poorly maintained and safety glasses broke the seal.

Most people don't wear ear plugs properly, he said.

"Unless they are custom-moulded ear plugs they are prone to be not sitting properly.

"Most left and right ears are different - it is like left and right feet - one ear might be fitted properly but the other is not."

Good design was the ultimate solution and because it sometimes came at a higher price, would not be chosen unless a company had a proactive health and safety culture.

Dr McBride was invited to Hawke's Bay by former OSH inspector-turned-consultant Miles Robinson, who said hearing loss was a significant national problem.

ACC claim costs for work-related hearing loss and traumatic hearing loss - which could be non-work related but resulting from an accident - was more than $39 million for 2016.

Hearing loss is becoming more widespread as the country ages.

A 2015 University of Auckland study projected a 74 per cent increase in Hawke's Bay people with hearing loss aged more than 65 by 2031.

It said New Zealand's median age increased from 29 years in 1951 to 37 years in 2011-12, and would likely increase to 44 years by 2061.

In New Zealand manufacturing industry represents about 25 per cent of all claims for noise induced hearing loss, more than any other industry.

The Occupational Safety and Health Service's Code of Practice sets a low bar. A 10 decibel hearing loss is predicted for 95 per cent of the noise-exposed population if they are exposed to the maximum allowable noise level eight hours a day for 40 years.

In New Zealand that maximum is 85 decibels averaged over an eight-hour period, with a peak of 140 decibels.

The code says once a company is aware it exceeds the limit ear protection is a temporary substitute until a noise-control programme is implemented.

The temporary removal of ear protection in a high-noise area dramatically reduces effectiveness.

"A worker not wearing a hearing protector for as little as 30 minutes a day can reduce by half the protection it is giving over the entire day."

Some industries are slower to address noise control than others. Dr McBride took part in the ACC study Noise in the Shearing Industry, where 40 shed measurements all exceeded the maximum noise level.

In none of the sheds was the wearing of ear protection witnessed during the study.

The ACC study said shearers suffered the most, suffering "near field" exposure from the downpipes containing gears near their ears and handpieces with chattering blades.

While the law says their employer is responsible for noise reduction, shearers own their own handpieces and farmers the shearing plant.

Shearing contractor and president of the New Zealand Shearing Contractors Association Jamie McConachie said the industry was aware of the problem.

"I'm half deaf, so what does that tell you? I think it is a bit of an issue."

He said ear protection was good health practice and good business.

"You have to look after your staff and to be honest it is only in the last 12 months I have started supplying earplugs to my staff. We have another health and safety meeting coming up and will probably look at when we will make it mandatory."

Taumarunui and Taihape shearing contractor Ewen Mackintosh made ear protection mandatory for his staff three years ago.

He said hearing loss was an occupational hazard "without doubt".

"Anyone who denies it is just pig-ignorant, as far as I am concerned.

"I know some people think I am just nuts and it is a waste of time but I do know of about half a dozen people who lost their hearing and shearing has been their main occupation.

"Most of the ones that were opposed seem reasonably happy wearing it now. Why wouldn't you? If you know the decibel reading is too high and you know you are exposed to it all day, why wouldn't you do something to look after your hearing?

"We got a bit of stick over it for a start but to be honest it is one of the things I am most proud of.

"The young ones coming into the shed, they won't wear them unless it is compulsory, so myself and my partner decided to make it compulsory."

He said he will never be thanked by his staff for not losing their hearing because people only think about hearing after it is gone.

Along with Dr McBride and Mr McConachie he identifies music in shearing sheds as a major problem.

Dr McBride said workers played music "so they can't hear the noise".

An ACC-funded Noise in Shearing Industry study said music in sheds was likely to be a complex problem to fix "but one which could reduce the exposures significantly for all the groups, those more remote from the shearing potentially gaining more benefit".

Mr Mackintosh said the music was sometimes at an "incredible level - like a nightclub".

"I don't want to take that away from them but perhaps they have to think about it a bit more."

His health and safety regime extended to other areas, such as regular breath-testing of van drivers so it was "a good safe outfit to work in".

"I can't see the point of keeping them safe in one area and neglecting them in others."