How to reduce machine noise ? This is a question in many contexts related to the application of Directive 2003/10/EC on the minimum safety and health requirements relating to the exposure of workers to the risks arising from physical agents (noise), transposed in French law by the Decree n ° 2006-892 of July 19, 2006 relating to the safety and health prescriptions applicable in the event of exposure of the workers to the risks due to the noise and modifying the Labor code.

Indeed, the exposure limit values ​​are set as follows: a daily noise exposure level of 87 dB (A) or a peak sound pressure level of 140 dB (C).

But the lower exposure values ​​triggering the preventive action provided for in Article R. 231-131 (1) (1), Article R. 231-133 and Article R. 231- 134, paragraph II, are lower, since they are fixed as follows: a daily noise exposure level of 80 dB (A) or a peak sound pressure level of 135 dB (C).

Therefore, it is important to know how to reduce machine noise, if its noise emissions are (as is often the case without soundproofing device) likely to impact the driving position or other nearby workstations in a workshop or in other work premises.

In particular, machines in the corrugated cardboard industry (e orrugators and processing machines), rotary presses in the printing industry, machine tools in the metalworking sector (presses, punching machines, milling machines), lathes) are noisy enough for the question to arise: how to reduce the noise?

Indeed, the list of machines being noisy by nature would be long to establish, covering very different realities in terms of sound emissions: concrete press (emitting low frequency sounds), woodworking machines (with high frequency noise), ultrasonic welders (to name a few) are some typical examples.

In many cases, the noise reduction of the mechanisms involved for the operation of the machine is a step being too delicate to be considered a posteriori (but it can usefully be considered at the design stage e.g. by favoring stop pieces in nylon rather than steel where possible).

Therefore, a usual way to reduce machine noise is to limit the propagation of its sound production by means of a protection (to which are associated several language elements e.g. enclosure, hood, carterization) able to oppose the transmission of sounds through it while avoiding the reflections of acoustic waves inside (the protection must be absorbent) and which must be sufficiently enveloping not to leave outside noise sources.

To reduce machine noise one must therefore use industrial soundproofing panels: some are modular and easily removable, what can be useful in case of modification of the arrangements envisaged at a certain time for sound insulation, and what is often imperative for maintenance (some panels are equipped with glazing, for the visual control of the production process by an operator).

In general, access must be managed (by means of doors or hatches e.g. pivoting, sliding in vertical translation).

The air renewal of such an enclosure must be taken into account, involving a soundproof air inlet and a soundproof air outlet, with a fan.

Sizing and generally technical choices in relation to the problematic of reducing machine noise requires multidisciplinary skills and the success of a project is promoted by the experience i.e. by the previous confrontation with the same problematic.

To reduce machine noise, one can solicit Isolation Technologie Services (ITS) which can perform acoustic measurements on site or base its worm on drawings, and offer solutions optimized for each context and subject to a guaranteed result .

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