Simplified Determination of the Environmental Correction for Noise Emission Measurements

A European market surveillance campaign, the NOMAD study, has shown that about 80% of the noise emission data for machines are not reliable. In order to enable small and medium-sized enterprises (SMEs) among the machine manufacturers to carry out sufficiently accurate, cost-effective measurements of their machines within their own premises, a simple procedure for the approximate determination of the environmental correction (K2) is developed. It is based on the method of qualifying the measuring environment according to ISO 3744 by means of a reference sound source (RSS). This expensive RSS shall be replaced by a small, portable and loud machine (substitute RSS) available in many companies. The sound power of the substitute RSS is determined by measurements according to the standard under approximated free-field conditions. With the aid of a subsequent sound power measurement in the room to be qualified, the K2 value is determined. We present criteria for the selection of substitute RSS and measurements, characterizing selected substitute RSS. The procedure is used to determine the K2 values of different rooms. Those K2 values are compared to those obtained with a professional RSS. Pros and cons of this procedure, especially with regard to practicality and sufficient accuracy, are discussed.