Industrial Noise
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Sounding-Off – occasional informal comments and opinions (rants). These are personal opinions and should not be construed etc … Please feel free to reply.

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Acoustic Shock – Shock!!

Doesn’t the term “Acoustic Shock” sound nasty? If you renamed it “unexpected somewhat louder headset noise than usual that is still at only a tiny fraction of the noise level that is deemed to cause hearing damage in industry”, it wouldn’t sound so bad. The problem is that there is something of a bandwagon with plenty of horror stories in the media about “acoustic shock” in call centres and you can find a lot of “information” on the web. I was even told by someone recently that an event was so bad for one operator that it “made her ears bleed” – apocryphal, but he believed it.

Headsets have limiters; people have volume controls. We’ve measured many call centre operator exposures and the highest still had daily noise doses in the mid 70s – 1/10th the level at which PPE is mandatory in industry. If the noise limiter on a station is not working, you could get startling events – easily solved by fixing the technical problem. The real problem is actually not so much technical and acoustic, but one or more of the human problems associated with poor working conditions that can cause stress. And unexpected acoustic events can cause stress in susceptible people that can lead to a range of stress related symptoms. Unless someone can show that the hearing of call centre personnel is an order of magnitude more sensitive than in industry, conventional hearing damage could only happen via a combination of faulty equipment and a long term commitment by the operators to working at a volume of 11 (Spinal Tap scale …).

Satisfying Super-Sensitive Complainants with Psychological Silencing

If you play white noise to a group of people and tell them that the song “White Christmas” is hidden in the sound, about 30% of them will be convinced that they can hear it. The human mind is always looking for patterns – even when they aren’t there. This propensity explains a significant proportion of complaints where noise levels are actually very low (they can be close to, or below, the threshold of hearing at low frequencies) or the complainant has mild tinnitus. The imagined pattern may be triggered by low level noise that isn’t itself the real cause of the subjective “nuisance”. Based on this understanding, we have developed an innovative solution based on “psychological silencing”. This involves broadcasting a carefully designed noise signature (matched both to the existing background and to the disturbing sound) from a bespoke sound system installed at the “culprit” site. This destroys any character in the sound and, coupled with an explanation and demonstration to the complainant as to how the “pattern” has been removed, they no longer hear it. Et – voila! No more complaints.

Plugging Entertainment Noise

Have you noticed that the PPE manufacturers are rushing out new devices – “now with added less protection” – for lower levels of noise exposure and for the entertainment industry? I can personally recommend these plugs for rock concerts – the music sounds better, but you do have to forgo the traditional post-gig head-buzz and “temporary” deafness. Talking of which, the new regs apply to entertainment from April 2008. If our experience is anything to go by, much of the industry still has its hands over its ears and is trying its best to ignore the whole thing…

Noise Kills – New WHO Data Quantifies the Risks

Noise is stressful and can damage your health – particularly if you show up at 3am to an all-night party asking them to turn the noise down… New evidence collected by the World Health Organisation indicates that c 3% of deaths from heart disease is attributable to long term exposure to environmental noise – mainly nighttime noise exposure, with 2% of the population suffering from severe sleep disturbance, 15% from serious annoyance and with additional significant effects on the learning abilities of children. As noise complaints in the UK have increased by a factor of 5 over 20 years, this indicates that the problem of LOUD NOISE is rapidly getting worse. Now for the figures: the threshold for cardiovascular problems is c50dB(A), with sleep disturbance at 42dB(A) and annoyance at 35dB(A) (all at night). 55dB(A) day or night has a negative effect on the learning ability of children (a 25% drop in long-term memory recall of children has been directly linked to the noise from a nearby airport). However: as these figures are all in dB(A) and a significant proportion of sleep disturbance cases involve low frequency noise that does not contribute significantly to the dB(A) value (think of bass beat, fan tones, transformers, combustion noise, distant diesel boom..), they must under-estimate of the scale of the problem. We were designed a few million years ago to have ears that stay awake at night and with a brain and body that react to sounds. This ability has obvious evolutionary advantages – a rapid change from a potential puma buffet into a fully leapt-up and running away type creature at the merest hint of claws on stone was a good thing for a small ape. Nowadays, however, noise can cause the associated stress hormones to circulate constantly which can cause long-term physiological damage leading to heart failure, strokes, high blood pressure and immunity issues. And that’s not counting the apoplexy brought on by the neighbours doing …. just about anything that you do, but obviously without the same consideration for others. Apart from the dog, which should be put-down…

Apparently, high levels of noise do not damage your hearing…

… as long as the “noise” is music. Thus spake Richard Littlejohn of the Daily Mail earlier this year – he’s a journalist, for some value of “journalist”. “Blessed is the man who, being ignorant, abstains from giving us worthy evidence of the fact” (with apologies to George Eliot). This journalistic licence is addictive, I feel better already….
Quoting RJ: “As the Mail [made up] reported earlier this week, one honk on a cornet is alleged to be enough to cause permanent hearing loss. Standing next to a saxophone is as dangerous as firing a field cannon.” “After just 19 minutes exposure to a school orchestra, you might as well start learning sign language and lip reading”. “Better still, why not just ban music altogether? That‘s what the real Taliban did… That way, no one will come home from school with his ears bleeding”. “..the trouble arises when elf’n’safety starts seeking out problems where they don’t exist and meddling in areas which are nothing to do with them..”. “HSE shock troops… more lethal than operating a pneumatic drill.. jumbo jet taking off.. earmuffs.. how are they supposed to teach when they can’t hear what is being played?”. Etc etc….

Back in the real world where the noise regulations now apply, I have measured the sound from orchestras and other musicians (and taken pleasure in winding-up prima donnas by referring to the “noise” from their virtuoso performances). Fact: music teachers and musicians can be at substantial risk of hearing damage (which is just a tad important given their occupations…). Also fact: reducing the risk is largely a matter of attitude and education coupled with a few simple precautions. My sons’ band members all wear ear plugs when rehearsing. I wear musicians’ ear plugs at rock concerts (which often improves the quality of the sound as your ears are no longer overloaded). One of the examples we use on our entertainment noise competency courses is a Notting Hill Carnival float at over 140dB – well into instant hearing damage territory.

If you’re to be true to your own “elf’n’safety” philosophy, it should be easy to persuade you to drive your own car at high speed with no seat-belt, disabled air-bag, no anti-lock brakes, at night, in the rain, with treadless tyres – and let’s add a loop of the greatest hits of Barry Manilow playing at full volume. After an hour, you’d be begging for hearing protection…. If we added a spike to the centre of the steering wheel (auto-kebabing), you’d drive more carefully – because you know it is dangerous.
So let’s not spoil the fun, monsieur Richard (may I call you Dick?). Let’s just help people in the music and entertainment industry, or those who have to work in places such as venue bars, avoid going deaf through simple (or, in this case, wilful) ignorance of the real and present risks….