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noise and vibration control


    Noise is unwanted sound. It can cause hearing loss, disturb verbal communication or cause nuisance. The most common sources are industrial noise and traffic. Vibrations can cause damage to assets, radiate noise or cause discomfort to people.

    Reducing the noise and vibration levels can be expensive, which makes the definition of allowable noise levels economically important also.
    For noise control on industrial sites two topics are central:

  • The allowable sound pressure on the site
    • Prevention of hearing loss
    • Speech intelligibility and communication interference
    • General nuisance
  • Nuisance to neighbors
  • From these laws and guidelines were developed. Guidelines provided by the World Health Organization can be found at Guidelines for Community Noise

    Noise Control Possibilities

    After the definition of the allowable levels an approach to obtain the required levels in the most economical way is needed. For a grass roots plant it is important to start the design process from an overall overview of the sources and the limits that they need to comply with. For this it is important to recognize the characteristics of different sources. For modifications to an existing facility the same principles apply, but implementation is limited by more boundary conditions.

    The place where noise abatement engineers prefer to reduce the noise is where it starts: at the source. If this does not lead to the desired result the noise can be abated at the transmission path. The last place is the receiver.
    In short this means:

  • Noise control at the source: design or select low noise machines
  • Noise reduction at transmission path: silencers, mufflers, mounting on vibration pads, enclosures, ...
  • Personnel protection: Ear caps or plugs

  • Project approach

    During project execution noise control is one of many things that need to be addressed. It cannot be seen independent from the safety and functionality of the plant, its lay-out, schedule and cost.

    Front End Loading

    During first phase of the front end loading the main interest is to decide if this is a project that the company wants to invest in and, if this is the case, to which capacity and where to build it. At the end of the Front End Loading the project should be defined, including noise control. This implies that first of all one needs to be sure what the allowable noise levels are, both from a legal and social point of view. Secondly, one needs to be sure that these can be met. For this the noise sources are evaluated and unsilenced level prediction methods are used varying from in-house correlations and experience data to vendor provided data. For dominant noise sources it is strongly recommended to make use of the vendor's knowledge.
    These values are used in computer programs that provide noise contour plots. The noise levels at the site and noise immission at the neighbors can be evaluated and the allowable level per source and/or required noise reduction can be judged.
    The front end loading will usually be completed with a noise control management sheet, which provides a maximum allowable noise level per source.

    Project Execution

    The noise control management data sheet is used as the input for equipment requisitions and specifications. Vendor quotations and guarantees need to evaluated. The noise control management sheet and associated calculations need to be updated with the selected equipment data. This will include good and bad news. In practice a number of dominant noise sources such as compressors or air coolers will receive most of the attention to obtain the goals.

    Noise Measurements

    One can specify and perform noise measurements at the workshop for individual items. After completion of commissioning and start up of the plant the noise levels on site and outside the fence can be verified. This can be demanded by the authorities.

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