This paper was written and presented by the principal of Camets Acoustics to "Environment '78". In 1978 the principal worked for the State Pollution Control Commission, NSW, the predecessor of the EPA, NSW. We feel that the content of this paper is as relevant today as it was in 1978.

Another piece of information worth looking at when considering planning is our Project Flow Diagram. This diagram illustrates the cost savings achievable when addressing acoustics early in a project.

1. Introduction

"Peace and quiet" - in our industrialised, mechanised and motorised society today the control of noise pollution, like many other good things, generally costs money. A quiet urban environment can only be achieved with the outlay of money and effort. But the cost effectiveness of noise control can and does depend dramatically upon the forethought and planning given to a project or development. If you want to save money on noise control it usually makes good sense to spend a little money (and a lot of thought) towards noise abatement in the initial stages of a project or development. To rectify a problem after it has been created nearly always costs far more in the long term and is far "less cost-effective". It "pays to plan".

The Commission (State Pollution Control Commission, NSW, the predecessor to the EPA) is well aware of its function in this and directs much of its attention toward, and promotes, areas where maximum effectiveness can be achieved; such as zoning of areas and vetting plans and designs prior to construction. Only by such means can we confidently hope to arrive at 'environment 2000' with many of the present day problems solved without enormous cost.

2. Noise Pollution Created by Improper Planning

There are many instances that can be cited where noise pollution could have been avoided by better planning.

No residential development should be contemplated adjacent to heavy industry. Figure one shows the difference in noise levels generated by some typical activities in heavy industry and residences.

A steel fabricating shop has many very loud noise sources, generally of an impact nature such as hammering, dropping of steel bundles and large plates, chipping of welds plus the screeching, grinding sounds of tortured metal.

The noise emitted from a forging works has both continuous, day and night sources as well as daytime loud impact noise sources. The loud deep roar of furnaces that are operated continuously to heat large metal ingots propagates over long distances and is quite annoying. The steam driven drop forge hammers propagate impact noises and ground vibrations. Large boilers associated with the forges with their intermittent duty emit large volumes of steam hissing through vents.

A processing plant has a mixture of the above noise sources and some additional ones such as the whirr of ventilation fans, hiss of steam and compressed air vents and the whine of motors.

Then there are other activities such as chemical processing plants that operate continuously seven days a week with high pressure air compressors, water chillers cooling towers, boilers, stirrers, motors and pumps located amongst complicated piped and open structures. Many items of equipment are situated in elevated locations in the direct line of site to many other premises without any barriers to reduce noise propagation.

Repetition manufacturers create many impulse noises, eg, metal stamping, extruding folding metal machines and air release jets used to automatically eject articles from various machines.

Concrete blockmakers and prestressed concrete panel makers using ear piercing vibrators to settle the concrete are the most disturbing. So are the ball mills and crushers used to grind rocks and various materials down to size as required in various industries.

Quite often the last straw is the punctuation of the day and the night by the sirens and hooters that break the workers day down into smaller segments. Coupled with this is the continual blasting from the public address systems above the roar of the work in many establishments.

Many of the industries cited above are located adjacent to or are surrounded by residences and have been the source of severe complaints and extensive investigation by the Commission to solve the problems.

Noises are frequently found to be at levels which have and interfere unreasonably with telephone communication, radio and television listening, and sleeping, not only during the night but day also. Sleep arousal in our complex noisy society is causing a problem.

I have found cases where people have had to resort to vacating their houses as a result of noise pollution emanating from nearby industrial premises. One such instance was where a truck driver was kept awake at night by the beating and whining caused by ventilation fans in a processing plant. Construction noise is sometimes a reason for people taking a sudden vacation.

3. Unsolvable Noise Problems

The prohibitive costs of redesign and complete replacement of noisy equipment which is performing an essential task frequently prevents adequate steps been taken to eliminate offensive noise.

Flares for burning off dangerous air pollutants, is a typical example. However, recently the frequency of high level flaring for one company was reduced by incorporating quiet ground furnaces into the process.

Noise control enclosures cannot be erected above certain chemical plant if there is a danger of explosion of vapours or gases. Natural ventilation is essential to prevent gas concentrations reaching explosive limits.

Where there is a danger to operators of any volatile gas explosions in furnaces all exits and passage ways are kept clear and unobstructed, thus noise is free to escape. These instances have occurred in multi million dollar plants developed adjacent to residential areas. Relocation is not feasible.

Large steel fabrication yards extending over acres of land cannot be economically enclosed to abate noise.

Garbage tips located in residential areas must be served by noisy garbage trucks, bulldozers and scrapers. Often suck items of plant cannot be economically silenced to the extent where they meet the residential noise criterion.

The location of truck access and egress routes in established factories is often decided by process of building constraints and becomes unalterable when construction is completed. If only more thought had been given to this problem at the planning stage it may have been avoided. Truck routes could have been away from the residences or even from another street.

4. Stages in Planning to Minimise Noise Control Costs

4.1 Land Zoning and Use

With an understanding of noise and its propagation, Town Planners could frequently eliminate noise problems before they start and at no real cost, by a noise zoning or planning approach. Refer to sketch one. By this means of grading the activities in order of the noise produced the maximum reduction of noise with distance can be obtained. Avoidance of most problems could be achieved. Note the use of buffer zones such as golf courses, gardens, libraries, museums, churches, interposed between major noise sources such as highways and heavy industry, and the quiet residential areas.

Land zoning is generally controlled in this State by the N.S.W. Planning and Environment Commission and Local Government. There are, of course, many factors to be considered in any land zoning scheme. But what is certain is that noise control should be a key factor for satisfactory cost effectiveness in noise control. It is often difficult from a noise viewpoint, to feel that zoning plans have managed resources to the best advantage of the available areas between where people live, work and play. Land zoning obviously needs careful assessment of noisy and quiet activities and the social values such as maximum travelling time that people are prepared to accept. How far are people prepared to travel for a quiet evening or weekend against the convenience of nearby work. The convenience of having recreational facilities next door despite some disturbance from them may be acceptable. Such values are often difficult to quantify. But the above broad principles of separating quiet and noisy activities has obvious and substantial benefits to the community in noise control cost savings.

4.2 Conceptual and design stage

In many instances when the plans for any industrial or commercial venture are being considered, noise control is overlooked or given only cursory thought. Yet it is at this stage, more than any other stage in the project, that noise control can be effectively implemented and costs minimised. Noise control should play a much more important role in layout and arrangement of plant.

It has been demonstrated that additional noise control, if properly considered at this stage, will usually cost less than 1 or 2% of the initial capital costs of buildings and plant.

The New South Wales Government in compiling the Noise Control Act, 1975, recognised the cost effectiveness of noise planning and thus Section 27 of the Act was introduced. Approval prior to construction of any new factory which could be described as scheduled premises is required under the Act. Likewise, occupants are required to apply to the Commission for approval to alter plant or install any new plant in scheduled premises if by doing so they are likely to cause or increase the emission of noise from those premises. Evidence of any necessary Local Government approvals must be sighted by the Commission prior to the issue of an approval under Section 27 of the Act.

The Commission has the overall authority, and is the only body authorised to control noise from scheduled premises, other government bodies and public places. Scheduled premises are those prescribed classes of works listed in a schedule and this schedule has been reproduced as figure two. Most large factories are included. Generally factories which use 50 kW or more of mechanical power or those that burn 300 Kg or more of combustible material per hour are scheduled.

Municipal and Shire Councils have authority to control noise from non-scheduled premises including domestic residences and smaller factories.

The Commission normally asks large companies to submit a noise impact statement with their application for approval, and will normally grant approval subject to certain conditions. Typical conditions may include; the types of materials to be used in the construction of the factory; specific noise control equipment to be installed; the times of operation of the plant or the times of acceptance of materials or the delivery of goods in large trucks. Noise problems are often overcome at the design stage simply by the strategic location of noisy equipment or plant further from noise sensitive areas such as residences, schools, and hospitals.

While the Commission stands on the side of the person whose environment is being polluted by noise, it is not unmindful of the costs of the control to the polluter.

To ensure that the acceptable noise criterion for a nearby residential area is not exceeded, the factory designer should employ the acoustical tool termed sound power. The acceptable sound pressure level at a given distance from the factory in simplistic terms can be expressed as an overall sound power level of the factory. This is an absolute measure of noise, which is quite independent of distance considerations and the environment in which the source is placed. If there are three equal noise sources on the premises, the specification of sound power for each source should be 5 dB lower than the overall sound power allowed. Each item of plant or equipment can be manufactured in different parts of the country to this specification, and the factory designer can be assured that if the purchase specification for each item has been meet, then the overall noise level of the factory will be acceptable. This method of planning and design obviates the unforeseen need for corrective noise control treatment after the installation has been completed and excessive noise levels encountered.

4.2.1 Better Factory Planning and Layouts

When the Town Planner unfortunately has not had the opportunity to grade the noise sources as indicated previously, it is left to the architects or engineers to alleviate potential problems for an industry located adjacent to a residential area.

In sketch two, a brick or concrete block structural wall has been used to screen the factory noise sources from the residences. The brick wall could be staggered and screened by trees to break up the size and monotony of such a structure. The area in front of the trees could be a play area for children as well as act as a potential buffer zone for noise.

To minimise noise control costs good factory planners will automatically locate the noisy sources behind screens and as far from residences or noise sensitive areas as possible. The design of the factory complex in sketch three shows the sensible use of a canteen, store, or office block as a barrier between the noise and the residences.

Finally a warehouse that supposedly has little or no noise generated by its operation, can be somewhat misleading. Here in sketch four we see a noisy forklift trucks required to shift materials. There are water chillers, cooling towers, refrigerants and compressors required to store goods inside the warehouse. Note, how all these items are located at the rear of the premises sheltered from the residences by the acoustic barrier of the building and stored goods inside.

Such means of controlling noise cost nothing but a little forethought.

4.2.2 Better Selection of Building Materials

Should the above materials not be sufficient, provisions should be made so that the properly designed acoustic enclosures can be installed, or silencers can be fitted to noisy equipment.

Inside a noisy factory, levels of 85 dB(A) may be unavoidable. If the factory is located near a sensitive area, a reduction of 30 dB(A) may be necessary. To achieve this, a 30 dB(A) enclosure is required. By reference to figure four it will be seen that a 100mm hollow concrete block wall rendered on one side is the minimum standard of construction.

One area where savings in noise control can be achieved is in the use of correct building materials at the outset. For instance, to change a 20 dB transmission transmission class cladding such as 0.8mm sheet metal to a 43 dB cladding such as 100mm solid concrete blocks, the costs can be very high. Besides the enormous cost that there is the time factor of rebuilding the structure and the inconvenience to disrupted production schedules. The rule in noise control is PLAN.... PLAN....... PLAN, all noise control measures first, not later and save a great deal of money.

Obviously truck access doors and ventilation and openings into factories must be provided but the location and size of these is critical from a noise viewpoint. Care should always be exercised in determining the area and location of such openings in any factories or building which is acting as a noise barrier to ensure that the acoustic performance of any structure is not degraded in a an unforeseen manner.

Reference to figure three will show that a total free area of only 0.1% to the total area of an enclosure will degrade a 40 dB transmission loss structure to only 30 dB.

Silenced natural ventilation cowls are available for factory buildings. The ventilators provide noise reduction of factory activities; better air flow versus the many axial roof fans required for the same duty; nil running costs; create no noise as axial fans do. In other words provide a savings in the long term. In one instance to install attenuators on to several axial fans located on the same roof meant completely reconstructing the building as well as providing good noise reduction of the factory noise for residences.

4.2.3 Vibration Isolation

Vibration isolation must be considered at the design stage.

Once a two metre by three metre block of reinforced concrete has been cast into the ground and integrated into a factory reinforced concrete floor slab, then a heavy drop press has been mounted on it, it is too late to consider isolation.

Any press which requires massive inertia block mounting to control vibration could easily transmit levels of vibration, that could cause discomfort in nearby residential premises. Refer to sketch five for a large drop press and inertia block which has been isolated to alleviate vibration transmission to nearby residences.

Particular care must be exercises where a factory floor is laid close to a water table since the resulting hydraulic pressure can transmit vibrations over great distances.

A solid rock strata foundation in the base of a quarry can transmit vibration over long distances and the source can in fact be hard to trace.

Even smaller machines such as refrigeration or air compressors are best isolated correctly at the initial design stage. The vibration caused by these small machines can be transmitted and converted by the enclosure panels, piping and other fittings into offensive noise.

After the construction has been completed, the retrofitting of springs and/or neoprene isolators may necessitate very expensive alterations to piping and duct work and incur costly production losses.

4.2.4 Machine Noise Design Constraints

Too often after the completion of installation, a machine having been designed to fulfil a mechanical function, and a noise problem is created, then only minor noise control measures are feasible. Often it is too late to achieve effective silencing and the environment suffers. Too often, the mechanical constraints on the size of the machine are too tight to allow panels to be constructed around the noise source. Instead of some of the complicated braced open side machine frames, a simple plate construction may be substituted and considerable noise reduction achieved.

Whenever I have been involved with designers who have an open mind and consciously consider noise control in their designs, they often achieve better articles and sometimes at lower costs with more contented operators of the equipment in the lower noise areas around the equipment.

If a machine has to be acoustically enclosed, and then ventilated as a result, the design of the fan impellers and motor should be carefully considered. It is possible in reducing the noise problem caused by the machine to create worse and more annoying tonal noise emanating from the ventilation system. Attenuators may be required as part of the installation.

The use of air blast jets for transferring small products can be quietened effectively by replacing them with pneumatic cylinders and rams. The reduction in noise achieved can be up to 30 dB(A) by the introduction of the quieter method of product transfer.

All exhausts from pneumatic equipment should be piped to substantial absorptive silencers. Probably only one silencer may be required in a factory if care is taken to avoid gas feedback into pneumatic equipment. Simple small pneumatic silencers near work benches tend to be failures as they disappear very quickly.

The noise created by high speed can or bottle runs (or conveyors) can be reduced substantially. Much of the noise is created by the clanking of cans and bottles together. The reduction of noise can be achieved at no sacrifice in the volume flow by using lower speed multiple or parallel path conveyors. Reductions of 20 dB(A) have been achieved with ten track slow speed conveyor instead of the original single track high speed conveyor.

The lowest possible peripheral speeds should be used on circular saws. The age old methods of tooth design and sharpening should be reconsidered. There are fairly well established techniques available to reduce the cutting noise by better tooth design. These better designs have achieved reductions in noise of up to 20 dB(A) inside a factory.

An important factor when considering the design of noise control equipment is that, ideally, the measures should become an indispensable part of the machine. An even better idea is to incorporate the noise control equipment as part of a Department of Labour and Industry requirement to operate the machine. If any panel of an enclosure has to be removed or dismantled for maintenance purposes and is not required to be fitted for the machine's operation then ion ninety percent of the cases the panel is left off after the machine's first or second maintenance.

One local instance of a properly designed and fabricated acoustic enclosure reduced the noise from a press by 15 dB(A). The enclosure replaced a number of metal grille safety guards. The enclosure was so designed that it had a counterweighted sliding front panel with a viewing window. The panel was fitted with microswitches to stop the press in the event of the front panel being opened to meet D.L.I. safety requirements. The interesting side benefit of this enclosure construction was that it saved in 'machine down-time' when a die was changed or adjusted. The old metal grille was secured by bolts. The safety guards required approximately two to three hours to remove and refit each time. A fork lift truck can now be used to remove the die directly once the panel has been slid up and out of the way. Noise reduction of 15 to 20 dB(A) have been achieved with such enclosures.

Should greater reductions of noise from the press be required attenuation must be given to proper vibration isolation of the press from the floor and also to counteracting the flanking transmission paths through the door slides, windows, material feed openings and product bin egresses.

5. Construction Stage

During construction many noise control measures that have been carefully designed are thrawted.

Careful supervision of construction work is essential. A solid panelled wall with a tested panel performance of 45 dB transmission transmission class may have an installed figure of only 25 dB. The downrating in performance being caused by a lack of attention to detail during construction. The loss of acoustic performance would only require the gaps in the wall to total 0.5% of the total wall area. (see figure four) This could easily occur in a factory wall where there are many ducts, pipes or electrical conduits passing through the wall. The total area of the gaps would need to be only half a square foot in the wall with an area of one hundred square foot. To overcome this loss in wall performance all holes, gaps around pipes, or joints between panels should be caulked and sealed so that they are airtight.

The majority of failures in achieving the specified performance of panels occur along the perimeter junctions between the walls and floor, ceilings, or other walls; and through the joints between the panels.

A good philosophy to adopt in noise control is that if you want to contain a noise inside an enclosure make the enclosure airtight for maximum effectiveness. It is bad economy to spend $10,000 on a brick and concrete plant room and only achieve the noise reduction performance of a tin shed.

6. Conclusion

In conclusion I would like to stress the importance of considering noise control prior to the event. That is plan to overcome potential noise problems at the design stages or earlier, when the costs of noise control are relatively inexpensive. The rule in noise control is PLAN.... PLAN.... PLAN, all noise control measures first, not later and save a great deal of money.

Sketch List

SKETCH ONE - Noise Source Activity Zones

SKETCH TWO - Factory Noise Sources Screened from Residences

SKETCH THREE - Factory Noise Sources Screened from Residences

SKETCH FOUR - Noise Sources Screened from Residences

SKETCH FIVE - Vibration Isolation

Figure List

FIGURE ONE - Typical Noise Levels

FIGURE TWO - Scheduled Premises

FIGURE THREE - Effect of Opening in Enclosures

FIGURE FOUR - Typical Noise Reductions for Common Building Materials

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