8. Results case studies ‐ design changes.
Design changes | |||||||||
Noise source | Intervention | Follow‐up | Initial noise level | Noise level after | 8 h TWA before | 8 h TWA after | Dose before | Dose after | Reference ID |
Roof bolting machine at underground coal mines | New drill bit isolator | immediate | reduced by 3.2 dB | MSHA PEL per hole 0.85% | MSHA PEL per hole 0.57% | Azman 2012 | |||
short term (after 253 holes and 628 m) | reduced by 2.2 dB | MSHA PEL per hole 0.9% | MSHA PEL per hole 0.66% | ||||||
4‐roll calender in a tire manufacturing facility "calender operator" | Replacing the piercer brackets, optimising alignment and improving preventative maintenance (increased and more frequent lubrication of the piercer and other areas of the equipment with high friction or pressure) | not reported | 87.7 dB | 86.3 dB | OSHA dose 72.8% | OSHA dose 59.6% | Cockrell 2015 | ||
4‐roll calender in a tire manufacturing facility "wind up operator" | Replacing the piercer brackets, optimising alignment and improving preventative maintenance (increased and more frequent lubrication of the piercer and other areas of the equipment with high friction or pressure) | not reported | 93.1 dB | 89 dB | OSHA dose 153% | OSHA dose 87.3% | |||
Heavy metal arms which drove the reciprocating blade on the machines | Alternative linkage using flexible nylon straps | not reported | 95 dB | 75 dB | HSE 2015 | ||||
Tobacco filter making machine | Machine design improvements on a tobacco filter making machine and room improvements | not reported | 9 dB reduction | Maling 2016 | |||||
Weaving machines | Use of different spindle | not reported | 100 dB | 90 dB | |||||
Locomotive for mining | Active noise control | immediate | Pan 2016 | ||||||
Mining truck | Active noise control | immediate | |||||||
Mining truck | active noise control and damping material | immediate | |||||||
Filler | Filler outfeed: line shaft removed, individual drives installed | not reported | 107 dB | 81 dB | Morata 2015 | ||||
Con‐air dryer | Machine set on vibration mounts, quieter blower | not reported | 94 dB | 85 dB | |||||
Transfer cart | not reported | not reported | 94 dB | 79 dB | |||||
Trimmer | rReplacing nozzles from trimmer with in feed decline drive belt | not reported | 98 to 113 dB | 86 to 104 dB | |||||
Continuous mining machine | Exchange of a single sprocket chain for a dual sprocket chain on a continuous mining machine (CMM, Joy Mining Machine 14CM‐15) | not reported | 93.4 to 93.3 dB | 92 dB | MSHA PEL 159 % | MSHA PEL 132.5% | |||
Moen case former | Exchange of pneumatic cylinder for servo‐mandrel | not reported | 97 dB | 87 dB | |||||
Cart | Exchange of cart wheels | not reported | 88 dB | 72 dB | |||||
Standard longwall cutting drums (mining) | Modified set of longwall cutting drums instead of a set of standard (baseline) drums | not reported | 98 dB | 92 dB | 95.7 dB | 93.1 dB | MSHA PEL 220.5% | MSHA PEL 158.6% | Thompson 2015 |
Haul trucks in underground metal/non‐metal mines | Improving the engine compartment noise barrier and changing the fan type, size, and rotation speed (larger fan of different design and different fan pulley to reduce the fan rotation speed to 90%) | not reported | 102 dB | 93 dB | MSHA PEL 495% | MSHA PEL 158% | |||
Load‐haul‐dumps (LHDs) in underground metal/non‐metal mines | Improving the engine compartment noise barrier and changing the fan type, size, and rotation speed (larger fan of a different design and a different fan hub to reduce the fan rotation speed to roughly 87% and new noise barrier material (Duracote Durasonic 5356)) | not reported | 98 dB | 96 dB | MSHA PEL 289% | MSHA PEL 231% | |||
Load‐haul‐dumps (LHDs) in underground metal/non‐metal mines | Improving the engine compartment noise barrier and changing the fan type, size, and rotation speed (a larger fan of a different design was installed as well as a different fan hub to reduce the fan rotation speed to roughly 95%) | not reported | 98 dB | 93 dB | MSHA PEL 289% | MSHA PEL 142% | |||
Standard camshaft washer drying nozzles (pneumatic) | Pneumatic nozzles replaced with suitable entraining units | not reported | 12 dB reduction | Wilson 2016 | |||||
Drier fan | Retro‐fitting aerodynamic and acoustic elements inside fan casings and the associated ductwork | not reported | 9 dB reduction | ||||||
Aluminium can extract and chopper fans | Fitting aerodynamic inserts inside the fan casing | not reported | 22 dB reduction | ||||||
Separator (large thin sheet distribution dome) | alteration to a vibratory separator: forming this component in stainless sound deadened steel | not reported | 105 dB | 89 dB | |||||
Metal trays | Replacing metal trays with plastic trays | not reported | 89 dB | 84‐85 dB | HSE 2013 | ||||
Metal wheels on baking racks | Replacing baking rack wheels with resin wheels | not reported | above 100 dB | 86‐92 dB | |||||
Loosening product from baking tins with air knives | Air knives modified to operate with a diffuse air jet | not reported | above 90 dB | below 85 dB | |||||
Bottles and cans banging together on conveyors | Fitted a pressureless combiner conveyor system | not reported | above 90 dB | below 90 dB | |||||
Baking tins banging together on chain or slat conveyors | Installing ‘tin‐friendly’ conveyors | not reported | above 90 dB | below 85 dB | |||||
Manual changeover of baking tins on conveyor | Installed robots to handle pans | not reported | 94‐96 dB | below 90 dB | |||||
Water pumps on filling machines | Replaced with air pumps and fitted silencers | not reported | 90 dB | 84 dB | |||||
Filling sachets and cups | New design of horizontal powder‐feeder and enclosed machine | not reported | 83‐84 dB | 80 dB | |||||
Bottle manufacture, filling and packing lines | Acoustic panels fitted to walls, high ceiling installed | not reported | Above 90 dB | 83 dB | |||||
Contact between metal trays and metal tracking | Replaced with plastic tracking | not reported | 94 dB | 87 dB | |||||
Product impact on metal chutes | Replaced with plastic chutes | not reported | 96‐98 dB | 90 dB | |||||
Electrically powered sausage‐spooling machines | Replaced with compressed‐air spooler | not reported | 86‐90 dB | below 80 dB | |||||
Tray‐indexing arm | Plastic caps on fingers of indexing arm | not reported | 94 dB | 87‐89 dB | |||||
Vibratory conveyor | Ensured conveyor only used at least noisy speed | not reported | above 90 dB | below 85 | |||||
Glass bottles on conveyor | New design of conveyor with different chain speeds | not reported | 101 dB | 84 dB | |||||
Lidding and de‐lidding tins | Installed robots to lid and de‐lid baking tins | not reported | 90‐93 dB | 88 dB | |||||
Number of cases: 41 | mean before | mean after | mean reduction | ||||||
Noise level dB | 94.5 dB | 85.3 dB | 9.6 dB | ||||||
TWA dB | 95.4 | 91.8 | 3.4 dB | ||||||
Dose % (OSHA) | 112.9 | 73.5 | 39.5 | ||||||
Dose % (MSHA PEL) | 207.8 | 117.6 | 90.1 |
MSHA = Mine Safety and Health Administration
OSHA = Occupational Safety and Health Administration
PEL = permissible exposure limit