A brief description of the requirements of the MD regarding noise
Machines and equipment must be designed and manufactured in such a way that the risk of noise hazard is as low as possible. Secondly the buyer or user must be informed about the amount of risk caused by the noise of the product. Therefor the machinery directive requires that noise levels must be determined by measurement and be declared in the manual and sales literature.
The noise level at a workplace of a machine (the emission sound pressure level) has to be mentioned and specified in the user manual if it exceeds 70 dB(A). Sound power has to be determined and declared if the emission sound pressure level exceeds 80 dB(A). These requirements for the manual have to be met for legitimate use of CE marking. The aim of the directive is that user and buyer must be able to assess and compare machines on all aspects of health and safety, including noise. The machinery directive does not contain any noise limits imposed on products within its scope. Legislative noise limits do exist for workplaces and for some machinery intended for outdoor use (2000/14/EU). Any other legislative noise limit depends on national laws. Some sector bound standards do contain noise limits, for example on Norwegian off shore (Norsok), or on breathing therapy devices (EN 17510). Also see: application guide of the 2006 directive.
The directive contains no guidance on the execution of noise measurements. Instead it refers to a set of harmonised standards. For fair comparison of products, noise measurements should be executed in a comparable way, thus safeguarding reproducibility. If the harmonised standards are discarded it takes a lot of extra effort to account for the relevance and validity of the specification thus obtained. Therefor the use of a harmonised standard is strongly recommended. We can investigate if noise measurement at your site is possible. This depends mainly on the ratio between the volume of the device under test and the volume of the measurement space (if indoor) and on the amount of acoustical absorption in that space. If the measurement can be executed outdoor then the background noise must be below certain limits.
The aim of the standards about noise measurement to which the machinery directive refers is to obtain results which make
comparison of the 'noise quality' of different products in the market possible. To achieve this the measurement should take
place in an environment almost equivalent to that of an open space above a reflecting surface. Also the operating conditions
must be reproducible, and preferable equal for all machines of the same family.
An open space above a reflecting surface can sufficiently be reached if the test object is small and the test room is
large and has at least some acoustic absorption. The standards give guidelines how the evaluate this.
Equal operating conditions can only be achieved if a more specific standard, a so called noise test code, exists.
A large number of noise test codes have been developed, and this process is going on.
Contrary to this the standard to evaluate exposure to noise at workplaces of an employee describes a measurement and investigation method which results in a noise level that is representative for a specific workplace, working environment, function, or group of persons. All factors in the environment which affect the noise level must be taken into consideration, something that must be strongly avoided if specifications of a machine must be established.
In 2013 the issue of noise declarations of machinery was evaluated by an EU workgroup. It appeared that there were many obstacles, and that only a small minority of devices were accompanied by fully compliant noise specifications. As a result the workgroup issued the NOMAD Guide for manufacturers, this gives an overview of the process and its pitfalls, and guidance how to comply.