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Noise emissions from machines - simple approximate determination of the environmental correction for the noise emission determination

Project number: F 2438 Institution: Federal Institute for Occupational Safety and Health (BAuA) Status: Completed Project


To enable employers to comply with their obligation to choose quiet machines, thus protecting employees against hazards due to noise at work, reliable noise emission data specific to the machines are required. Among other factors, the complex and high-cost normative measuring procedures for determining noise emission values are frequently considered as a possible reason for missing or unsatisfactory noise emission data. For small and medium-sized enterprises (SMEs) self-performed measurements in their own premises would be a practicable and cost-effective alternative. However, these frequently fail due to the necessary determination of the environmental correction of the room in which such measurements shall be carried out. The objective of this project therefore was to develop a simple method, practicable for SMEs, to determine the environmental correction.

A possible procedure for qualifying the measurement environment uses a reference sound source (RSS). The idea is to use a small, portable, loud machine available in every company as a substitute RSS instead of an expensive RSS. The sound power level of this substitute RSS is initially determined through measurements in the acoustic free field, which are carried out according to a noise emission measurement standard. Subsequently, the substitute RSS is placed in the room in which all machines of the manufacturer are to be measured. There its sound power level is measured again. Since the sound power level determined there is higher than in the free field due to sound reflections in the room, the approximate environmental correction for the test room is derived from the difference between the two sound power levels.

During the project, it could be demonstrated that this method generally achieves a sufficient degree of accuracy in determining the environmental correction. A checklist developed in the project helps selecting a machine available at the company which is suitable as a substitute RSS.

The use of machines already available at the company as a substitute RSS makes it easier for machine manufacturers to determine the sound power level of their machines in their own premises. This will help to declare the noise emissions of machines according to the requirements of the Machinery Directive 2006/42/EC in the future. As a result, companies will be able to procure quieter machines and thus reduce the noise exposure of employees.


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