As one of the world’s top racing engine design and manufacturers, noise levels have always been an issue for Ilmor Engineering. However, when the company won a contract with US giant, General Motors, to design and manufacture a turbo-charged V6 racing engine for the 2012 IndyCar championship, its managers knew that this would result in increased noise levels across the manufacturing and testing departments.

At the time, the company’s existing noise management system split the factory into ‘Zones’ based upon the noise exposure levels. The main machine shop was mostly Zone 0 – or where noise levels are below action level 1 / 80dB(A).

Additional machine tools had to be installed, adding to the noise background levels. These additions speeded up production, but had the potential to ‘tip’ some of the machine operators working in Zone 0 or exposure above 80dB(A). 

Nick Phillips, manufacturing manager explained: “When employees are loading and unloading work into the machine, an air gun is used to blow the swarf and excess cutting fluid from the machine. This generates high levels of noise, albeit of short duration, so hearing protection was used by our operators to control their levels of exposure to noise.”

To determine whether workers were being exposed to levels above 80dB(A) a repeat occupational noise exposure survey was carried out using a Cirrus Research doseBadge. This is a wireless personal noise dosemeter that can be used to carry out noise measurements in occupational and industrial hygiene.

By using a doseBadge, accurate measurements and recording of employees’ long term exposure to noise were tracked and analysed as that poses the greatest risk to an employees’ hearing and physical state.

The doseBadge can be set up to meet almost every occupational or industrial hygiene noise measurement standard, as well as EU Physical Agents Directive and the 2005 Control of Noise at Work Regulations (UK).

From the measurements taken at Ilmor Engineering, it was found that there were several points throughout the day where noise exposure levels would greatly exceed that of 80dB(A); at one point, noise exposure reached 110dB(A). 

As an interim measure, Ilmor issued instructions to those operators directly affected to wear their hearing protection for the complete shift, not just when loading and unloading work. 

After analysing the graphical traces produced by the doseBadge, it was also suspected that the principle reason for the rise was due to the increase use of the air guns and associated high levels of noise they produce.

A more detailed investigation was undertaken using a Cirrus Optimus Red sound level meter which enabled measurements to be taken of the instantaneous peaks and at a range of different frequencies. 

The Optimus Red has a clear, high resolution OLED colour screen, a wide 120dB measurement span (up to 140dB(A) and 143dBc Peak and simultaneous measurement of all available parameters.

Results from the Optimus survey were similar to those previously recorded; the main difference was that there were significantly more occurrences of the air gun being used per shift and the noise was affecting nearby operators.

Due to the logarithmic nature of noise exposure, it only takes a few extremely high levels of relatively short bursts of sound, lasting for seconds not minutes, to make a significant impact on an operator’s overall daily exposure. For example, exposure to noise levels of 107dB would mean an operator would receive their daily dose in as little over 3min. So, the increased exposure levels recorded by the doseBadge were directly caused by the increased rate of production and directly attributable to the increased use of air guns.

Due to the detailed and accurate information provided by both the DoseBadge and Optimus Red sound level meter, Ilmor Engineering was able to investigate and modify its manufacturing processes, taking noise levels back down to previous levels. 

Nick Phillips concludes: “Without the use of Cirrus Research’s noise measuring equipment, we wouldn’t have been able to find out the extent to the levels of noise our employees were being exposed to. The equipment was easy to set-up and use, and gave the readings and results that we needed to manage the workforce’s noise exposure and to implement appropriate hearing protection. The Optimus Red and doseBadge, contributed to us fulfilling our responsibility towards the environment and employees, ensuring noise produced by our activities was minimised.”