Posted on: Oct. 27, 2014
CIEH 2014 conference paper highlights the woeful ignorance and performance of the industry…
The paper given by Peter Wilson (INVC technical director) illustrated that a very large proportion of the environmental “noise industry” is woefully ignorant both of the proper diagnostic techniques and of modern noise control methods. Consequently, thousands of people are needlessly exposed to stressful noise over very prolonged periods. This results in unnecessary deaths from stress as highlighted in the recent BMJ and WHO reports (see “Stressed to death by noise” post).
The final straws that triggered the submission of the paper to the CIEH (see end of post to view a copy) were several truly awful reports from noise consultants and a series of noise control recommendations that were not only completely wrong, but also incredibly expensive.
Noise Reports – 2/10, could do much, much better…
We get many reports forwarded to us for comment, many of which are very dire indeed. Typically, as a result of noise complaints, a company employs a consultant in order to find out what they should do to reduce noise levels so that the complaints cease. A BS4142 assessment is carried out. The conclusion is that “complaints are likely”(!!!) – but with little or nothing in terms of how to eliminate the problem. Moreover, the reports themselves are often very badly written (one EHO delegate estimated that over 80% of the noise reports he sees are terrible…), full of extracts from standards, glossaries, calibration certificates etc etc, but little of substance in terms of suggested actions.
Diagnosis – fail
There is an unhealthy obsession with BS4142 – because it exists. Whilst it may be useful in some instances, the key to solving any noise problem causing complaints is to diagnose and rank the precise noise feature(s) that are the cause of the problem. In many cases, this is not dB(A). When a complainant talks of a low frequency hum, BS4142 and dB(A) are inappropriate tools that are still used time and again (although the latest update to BS4142 does include narrow band criteria – we will await the effect on general practice with baited breath…).
Best practice is to carry out a narrow-band frequency analysis which allows you to determine the precise frequency and to link it directly to the mechanical or aerodynamic features of a particular noise source. Quick, simple and accurate. However, the vast majority of consultants never even consider this approach, seeming to feel that 1/3 octave (or even 1/1 octave) is actually useful where there is tonal content. This is the 21st century. You can get narrow-band FFT analysis apps on your phone for free. There is no excuse for this level of incompetence. dB(A) is fine for simple broadband noise, but where there are tonal or temporal features, these must be identified and related to the subjective impression of the complainant through proper diagnosis.
Examples:
- Multi-storey office block; complaints about low frequency noise from nearby residents; based on dB(A), consultants recommend replacing chiller on roof; 7dB(A) quieter; complaints unabated as it was the wrong chiller; tonal analysis would have revealed the cause; best practice solution would have cost c £5k – £8k
- Complaints about industrial cooling tower tonal noise; “expert” suggested replacing whole fan unit at £31k as “no other solution practical”; emailed video sound track diagnosis revealed problem to be gearbox tooth-mesh; box replaced <£3k.
Noise Control – fail
The mantra seems to be: barriers, enclosures, silencers and lagging. Period. No attempt to identify and fix the precise cause of a noise problem, just try to hide it. Even when it works, it is typically an order of magnitude more costly than modern engineering techniques. Low-frequency noise from chiller plant: put a barrier in front – despite the fact that the laws of physics tell you that it cannot work. £20k wasted. Roof-top fans feeding directly into a short stack: lag the fans and ductwork – despite the fact that looking at a photo of the set-up would tell you that it cannot work as all the noise is radiated from the stack outlet. £50k wasted.
Examples:
- New thermal oxidiser plant problem; earth berm suggested @ c £100k (most noise from stack, so no effect); fan modifications, speed change, conversion of duct into silencer; 15dB(A) reduction and no tones; <£10k.
- Cardboard corrugation plant; conversion of building into enclosure recommended at £150k; best practice – modify machines at source at cost of £25k – also removed requirement for hearing protection.
- Large fan tonal noise problem; consultant recommended £100k of modifications (no tonal analysis made); <£7k aerodynamic fan modifications eliminated problem at source and reduced fan power consumption – paid for itself in 9 months.
- Burner noise; recommended building modifications at eye watering cost; yoghurt pot fitted inside burners solved problem…
More best practice environmental noise control case studies are available here.
And the consequences are…
Many of the projects in which we are involved have been problems for a long time, sometimes a very long time (10 years…). In most cases, they should have been solved in a matter of weeks. Time and again, the etiolation of the project has been caused by a combination of poor diagnosis and the high projected costs of suggested noise control measures due to ignorance of modern engineering techniques. Companies naturally baulk at the prospect of paying out large sums of money with no guarantee of success. In many cases, they have already spent substantial sums of money to no avail. The legal system beckons – with more costs and more delays. When we apply the diagnostic tools to provide them with a no cost second opinion proving that the problem can be solved quickly and at low cost, it usually is.
The consequences of the general lack of diagnostic capabilities and engineering knowledge in the environmental noise industry is that thousands of people are subjected to unnecessary noise induced stress over prolonged periods and that industry, shops, offices, hotels etc spend far too much on noise control measures that don’t work or are not best practice.
No cost review of diagnoses and noise control options v current best practice
Get a second opinion by email on what constitutes Best Practicable Means…
An EHO or organisation can forward noise data, photos, reports etc to us by email for a second opinion as to what constitutes best practice – at no cost. This has saved 50% – 110% of the cost and reduced the time-to-resolution (to the relief of those affected by the noise) by 60% – 90% across a wide range of projects. Alternatively, you could save time by getting a first opinion… Contact us for more information.
Potentially useful INVC resources
Remote Control of Noise by Email – click to solve
We have developed the technology to generate detailed best practice noise control recommendations based solely on information sent by email, saving time and money. A few pictures, a couple of noise readings and a Smartphone recording are often all we need – and the service is free. We’ve used this approach on projects across the world, from small restaurants in the UK to a mine in Australia to saving BP in the USA over $1 million on a $1.25 million fan noise control project (see our Remote Control of Noise section). Contact us for more information.
Would you like to find out how to evaluate best practicable means?
We have a one day workshop (“one of the most relevant and informative courses – thought provoking”: Cusack, Fareham BC; “the best lecturer I’ve ever had – with relevant case studies”: J Tofts, PPC officer) which can be run locally at low cost. More information on the Noise BAT / BPM training workshop.
Download the presentation here >>
