Noise and machine directive, measurement and CE marking.

Noise doesn't sell

A brief description of the requirements of the machine directive 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 machine directive requires that noise levels must be determined by measurement and be declared in the manual.

Declaration in the manual

Noise levels (sound pressure level) at workplaces have to be mentioned and specified in the user manual if they exceed 70 dB(A). Sound power has to be mentioned if the noise level at a workplace exceeds 85 dB(A) (or 80 dB(A) according to 2006/42/EC). 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 machine 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).

Relation between directive and standards

The directive contains no indications how to conduct noise measurements. Instead the directive refers to a set of harmonised standards. For fair comparison of products, noise measurements should be executed in a comparable way. 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. For the two reasons mentioned above the use of a harmonised standard is therefor strongly recommended.
Technisch bureau van Eeden is specialised in noise measurement on site. We gladly investigate if noise measurement at your production site is possible within the acoustical limits set in the harmonised standards. These limits depend 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 this space. If the measurement can be executed outdoor then the background noise must be below certain limits.

Measurement

The aim of the standards about noise measurement to which the machine directive refers is to have 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 be sufficiently be reached if the test object is small and the test room is large and has 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 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.