Measurement of leaks in air handling systems

One of the obligations of manufacturers and importers is market only safe products in the Czech Republic and in the EU. Pursuant to Directive 2006/42/EC (Government Regulation 176/2008 Coll.), the manufacturer or importer must, among other things, inform the users in the instructions for use of the noise levels emitted by machinery.

Another of the obligations of the manufacturers and importers of machinery for the products marketed in the Czech Republic and in the EU is to demonstrate conformity with the requirements of Directive 2000/14/EC (Government Regulation 9/2002 Coll.) in terms of noise emissions of equipment used outdoors.

What is tested:

• Noise emitted by the machine at the operator’s station and in the working space designed for the movement of the operators (sound pressure)
• Calculation of the sound power level of the machine
• Airborne noise emitted by household appliances
• Determination of sound power levels of noise sources using intensity probes – measurement by scanning
• Sanitary measurement of noise to verify compliance with the requirements of Government Regulation 272/2011 Coll.

What is assessed:

When measuring noise levels, a number of conditions must be met:

• Size of the environment with respect to the machine
• Materials used for the walls, ceiling, etc.; presence or absence of other objects in the room where the machine is installed
• Measurements are conducted at specific points as determined by the standards
• Measurements are conducted at each point for periods from 10 s (steady noise) to extended periods corresponding to the operating cycle of the machine - often with an impulse component - e.g. forging presses, etc.).
• Many C-type standards prescribe the activity to be conducted by the machine during the measurement of noise (e.g. size and type of the material being worked, type and speed of the tool, travel speed etc.).
• Measurement of sound power using an intensity probe places less demanding requirements on the acoustic environment than sound power measurement. The measurement will also provide information about the direction of the source of noise and will allow locating the points of the source of noise on the measured surface.

Most frequent problems:

• Improper environment (large machine in a small area)
• Too noisy background (in most cases, the level of noise of the background must be at least 3 dB lower than the noise of the machine; some measurements require a greater difference)
• Measurement using intensity probes requires a minimum distance of 1.5 m between the source(s) of noise and the reflective wall.

Standards:

• ČSN EN ISO 3744:2011 Acoustics. Determination of sound power levels and sound energy levels of noise sources using sound pressure. Engineering methods for an essentially free field over a reflecting plane
• ČSN EN ISO 3746:2011 Acoustics - Determination of sound power levels and sound energy levels of noise sources using sound pressure - Survey method using an enveloping measurement surface over a reflecting plane
• ČSN EN ISO 11201:2010 Acoustics. Noise emitted by machinery and equipment. Determination of emission sound pressure levels at a work station and at other specified positions in an essentially free field over a reflecting plane with negligible environmental corrections
• ČSN EN ISO 11202:2010 Acoustics. Noise emitted by machinery and equipment. Determination of emission sound pressure levels at a work station and at other specified positions applying approximate environmental corrections
• ČSN EN ISO 11546-2:2010 Acoustics. Determination of sound insulation performances of enclosures. Measurements in situ (for acceptance and verification purposes)
• ČSN EN 12102:2014 Air conditioners, liquid chilling packages, heat pumps and dehumidifiers with electrically driven compressors for space heating and cooling. Measurement of airborne noise. Determination of the sound power level
• ČSN ISO 9614-2:1997 Acoustics. Determination of sound power levels of noise sources using sound intensity. Measurement by scanning
• ČSN EN ISO 9614-3:2010 Acoustics. Determination of sound power levels of noise sources using sound intensity. Precision method for measurement by scanning
• ČSN EN ISO 11204:2010 Acoustics. Noise emitted by machinery and equipment. Determination of emission sound pressure levels at a work station and at other specified positions applying accurate environmental corrections
• ČSN EN ISO 11094:1997 Acoustics. Test code for the measurement of airborne noise emitted by power lawn mowers, lawn tractors, lawn and garden tractors, professional mowers, and lawn and garden tractors with mowing attachments
• ČSN EN 15036-1:2007, Annex A, Annex C, Art. 4.3. Heating boilers. Test regulations for airborne noise emissions from heat generators. Airborne noise emissions from heat generators
• ČSN ISO 7960:1997 Airborne noise emitted by machine tools. Operating conditions for woodworking machines

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