Selection of Quiet Machines
The noise exposure of employees can be reduced significantly
A machine characterised by low noise emission values pays off for two reasons: it results in a lower noise exposure of the employees at the workstation on the machine, as well as at adjacent workstations.
Machine manufacturers are required by law to provide information on the noise emissions of their machines in the form of a noise declaration. As a consequence, the noise emission values must be provided both in the operating instructions and in the technical sales literature (brochures and catalogues containing technical information). This is intended to render the machine market more transparent for the purchaser regarding the noise emissions of the machines and the purchaser is enabled to procure machines with lower noise emissions by comparison.
Thus, the following is applicable: purchasers and operators of machines should require the manufacturer to provide such noise emission information when procuring new machines.
The purchaser should request the following information:
- emission sound pressure level LpA (must be specified additionally by the manufacturer if the value is over 70 dB(A))
- sound power level LWA (must be specified additionally by the manufacturer if the emission sound pressure level LpA for this machine exceeds 80 dB(A))
- emission peak sound pressure level LpCpeak (must be specified by the machine manufacturer if the machine generates sound impulses (e.g. bangs) exceeding a value of 130 dB(C))
Measuring noise emissions
Here it is important that the specified noise emission values are determined under defined operating and installation conditions. This is always the case if the manufacturer refers to a corresponding machine-specific safety standard. These European standards mostly include a noise testing section indicating the necessary specifications for noise emission measurement, declaration and verification.
If a machine-specific safety standard does not include a noise testing section, machine-specific noise testing standards are applied. Ultimately, one of the basic standards for noise emission measurement may also be sufficient. For example a standard from the series DIN EN ISO 3741-3747 for the sound power level and DIN EN ISO 11201-11205, respectively, for the emission sound pressure level, including a declaration of the operating and installation conditions applied during noise emission measurement. Here the operating and installation conditions must be selected in such a way that they describe typical operations which are as loud as possible.
In individual cases, it may be expedient to have noise emission values for the planned use delivered in addition to the standard-compliant noise emission specification, upon consultation with the machine manufacturer.
Declaration of the noise emission
A reference to a standard is always decisive to be able to assume a sufficient quality of the specified noise emission values. DIN EN ISO 4871 plays a special role in this in particular. This standard listed in the official journal of the EU for supporting the machine directive does not only provide examples of a proper noise emission specification, but also defines verification procedures that should be used if there are doubts regarding the noise emission specification of the manufacturer. If, additionally, it is not clear whether the noise testing standard or a mentioned machine safety standard with noise testing section actually applies to the respective machine, this may be checked by having a look at the standards database (NoRA) of the Commission for Occupational Health and Safety and Standardization (KAN).
Furthermore, one should absolutely ask for the noise emission values of machines with particularly low noise emissions (low-noise products), because the manufacturer is frequently able to offer particularly noise-reduced versions of the corresponding machine.
Declaring the noise emission (LWA, LpA) is necessary in order to
- perform a risk assessment pursuant to LärmVibrationsArbSchV (German Ordinance on Occupational Health and Safety concerning Noise and Vibration Protection),
- be able to compare the noise emission values of the different makes with one another and thereby be able to select the machine with the lowest noise emissions in comparison,
- be able to compare the noise emission values of the machine coming into question with the noise emission data collections of the corresponding machine group regarding the state of the art.
Quiet machines ultimately cheaper!
Data collections regarding the noise emission of certain machine groups support the evaluation of the noise emission of the respective machine. When considering noise emission values of a machine group measured in accordance with the same standard, you will notice that the emission values of the machines offered in the market with the same output and under comparable operating conditions differ by 5 to 20 dB.
Moreover, the following is apparent: low-noise machines are not necessarily more expensive. Quite the contrary. Purchasing a low-noise machine frequently renders additional, expensive noise reduction measures in the company unnecessary. Upon reversion, the following is applicable: measures taken retroactively are always more expensive!
It is worth exploiting this noise reduction potential when purchasing machines (see Association of German Engineers [VDI] guidelines: emission of technical acoustic sources (Emission Technischer Schallquellen - ETS). It is recommended that purchasers of machines use the "Geräuschdatenblatt für die Beschaffung von Maschinen" (noise data sheet for procuring machines) (see German website) in order to request information on noise emission values from machine manufacturers.