Buy Quiet

Extensive and very detailed diagnosis and analysis techniques led to the devlopment of an engineering noise control at source kit for this Molins making machine. It reduced the noise by 4dB(A) at very low cost and without affecting normal access or operation (unlike previous suggestions involving acoustic screens) which was sufficient to avoid mandatory hearing protection.

It was licensed by the manufacturer so that they could provide a very profitable retro-fit or overhaul option service worldwide. This illustrates the commercial opportunities inherent in the engineering noise & vibration control technology in which we specialise.

Vibratory separator, screen or sieve noise is traditionally difficult to reduce as it is often predominantly a low-frequency issue. However, we have developed a range of elegant, low-cost engineering solutions that have wide application are are ideal for both as retrofit to existing units or that can be designed-into products at virtually no cost.

In this case, vibration was fed into the product via the separator drive and there are structural components that radiate noise. The trick is to ensure that as much of the "working" vibration as possible is fed into the product and that the spread of extraneous higher-frequency vibration is minimised.

We developed engineering source control techniques for the manufacturer of a range of vibratory separators, screens and sieves that could be built-in to their products without affecting access, maintenance or normal operation. These reduced the vibrating screen noise by 5dB - 12dB(A) at source at very low cost and without compromising hygiene or machine performance.

In this example, the noise control features included adding a high level of constrained layer damping to the sieve body itself and developing a spun laminated steel bowl to reduce impact noise.

This approach can also be used to develop low-cost engineering retrofit modifications for vibrating sieve or separator noise reduction.

Contact us if you'd like to discuss a particular project.

We have also generated a comprehensive technical note on all aspects of vibrating bowl feeder, hopper, conveyor and screen noise...

Other examples of our engineering vibratory system noise reduction technology include:-

• Record-breaking vibrating screen / sieve noise control
• vibratory hopper, feeder, grader, conveyor noise reduction

This suction fan used in a newly designed, automated pick-and-place system for food packets on a production line generated high levels of noise. Conventional fan silencing would not only have posed a hygiene problem (attenuators make use of porous acoustic absorbent materials), but would also have required acoustic enclosure.

We re-designed the fan mounting system (interestingly, the fan itself was designed for model aircraft engines) and modified the geometry slightly. This reduced the fan noise at source by 8dB(A) without affecting the efficiency of operation - and at zero cost once designed-in to the unit.

Weighing machines for the confectionery industry are a very common noise problem. In this case, the purchaser had implemented our Buy Quiet policy for new plant, with a target of 75dB(A) for this particular installation. One of our engineers attended the new machine proving trials at Easiweigh as part of the purchasing policy process to determine what would constitute best practice to meet the noise specification. We developed a set of modifications that reduced the initial 83dB(A) Leq noise level down to the required 75dBLAeq.

The low cost, high hygiene modifications included replacing the conventional (and non-hygienic) damping materials with much higher performance stainless constrained layer damping. This has since been adopted as standard practice on all new weighing machines.

A major customer implemented our Buy Quiet purchasing policy and passed-on to the supplier a request to reduce the operator noise levels from 90dB(A) down to below 85dB(A) in the production environment. We were retained by the manufacturer to provide design improvements as part of the of the machine development programme. Our engineering recommendations reduced the machine noise down to 82dB(A) at a cost of around £300 per machine (c 2% of the capital cost) without affecting normal operation or access. Modifications included sewing machine damping, control of exhaust air and minor changes to the machine base.

The purchaser of several multi-spindle auto lathes was on the point of cancelling the order as the first completed machines did not meet the agreed noise level of 83 dB(A) (3000 rpm) – they were typically generating 87 – 90 dB(A). We used the results of sophisticated noise and vibration analysis to recommend a change in the assembly procedures used that reduced noise levels to <83dB(A) at negligible cost.

The diagnosis and recommendations were completed in less than 2 days and, as a result, all purchasers now receive quiet machines. This illustrates the benefits of effective policing of purchasing requirements.

The most compromising and common issue we encounter is that plant noise data (fans in particular) never includes frequency signatures. Octave bands: yes. Narrow band (that defines if there is a tone): no. If there is a tone, in the UK it attracts a 6dB penalty – which only puts your predictions out by a factor of x4! Consequently, if you want to play safe, you over-engineer mitigation which adds a massive cost overhead. This is unacceptable. We try to get round this by asking for a smartphone recording from an installation anywhere in the world so we can design the optimum noise control measures.

This is a ridiculous state of affairs considering that you can do an accurate narrow band tonal analysis with a smartphone app for free. Noise consultants are also to blame as only a very small proportion of them carry out tonal analyses.

A detailed environmental noise impact assessment established 24 hour target noise levels for a new quarry as part of the planning submission. This was supported by predictions of the changes in the local noise environment throughout the working life of the quarrying project and a detailed compliance verification procedure.

Detailed Buy Quiet noise purchasing specifications were provided for every piece of plant to be installed within the quarry. These included the measurement procedures and the best practice noise control measures that should be used by the suppliers to ensure that the target noise levels were met as cost effectively as possible (most suppliers have very little knowledge of noise control engineering technologies).