Top 10 Noise Control Techniques
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Noise Control - Best Practice
.. + innovative "magic bullets" that may make you think...
noise
Low cost, DIY engineering best practice for common noise problems
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Industrial Noise and Vibration Centre: Slough www.invc.co.uk
The “You must control Noise at Work Regulations”
fan installation details
simple ductwork silencing
fan speed
pneumatic exhausts
pneumatic nozzles
damping - chutes, hoppers, guards...
vibration isolation pads - motors, pumps...
upgrade existing guards
chains and toothed belts
quiet motors - buy quiet
retro-fit fan modifications
yoghurt-based combustion
noise control
bolt-on quiet
free collateral quiet
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www.invc.co.uk
Top 10
Noise Control
Techniques
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Top 10 Noise Control Techniques...
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Placebo Silencers
“… these regulations are concerned with controlling noise, not measuring it ..."
Hearing protection can no longer be used for long term risk management
unless it can be proved that noise control is impractical
Companies should not repeat risk assessments that do not include useful
and practical information on noise control
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Companies should carry out a Noise Control Audit
assess the noise control options using the best of current technology
generate cost v noise reduction trade-offs for each item of noisy plant
plan the most practical and cost effective noise control programme
Copyright 2009 INVC www.invc.co.uk 1753 698800
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Top 10 Noise Control Techniques
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k14
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Noise Control is ....
Self-Financing Noise Control
Improved efficiency / productivity due to noise control modifications.
One company had spent £1,600,000 on acoustic enclosures. The Noise
Control Audit and subsequent testing proved that using BPM would have
saved over £1,000,000 and noise levels would have been substantially
lower and operating costs would be significantly reduced (down-time).
Noise control is not a safety issue
Noise control is an engineering problem that should be solved by
engineering means, in particular through noise control at source.
Noise source category
Effective noise control must be based on an accurate diagnosis and
not on assumptions
Pay-back Period
4 weeks
vibrators
fans
All the options must be considered, not just the conventional high
cost palliatives of enclosures and silencers. These techniques should
only be used where it can be proved that there is no engineering
alternative.
weighing
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20
40
Noise control costs - £000's
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Noise Control - Best Practice
higher efficiency, no cleaning
3 years
cleaning down-time reduced
2 years
presses
0
1 year
1 minute...
burners
60
80
conventional
doubled through-put
avoided being shut-down...
no enclosures, reduced down-time
100
best practice
Fan Designs
noise
axial fan - quiet impellor
centrifugal fan
Industrial Noise and Vibration Centre: Slough www.invc.co.uk
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Fans
Copyright 2009 INVC www.invc.co.uk 1753 698800
5-8
Top 10 Noise Control Techniques
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m15
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Centrifugal Fan Installation
m16
Axial Fan Installations
NOISY
QUIETER
high pressure
NOISY
low pressure
>2-3 duct diameters
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m35
Fan: Outlet dampers
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QUIET
m20
Henhouse
Copyright 2009 INVC www.invc.co.uk 1753 698800
Stalag Chicken-Run
Up to 19dB tonal reduction from axial fans via modifications to existing fan
ductwork to improve flow conditions. As the main neighbourhood complaints
were about the 62.5Hz tone, this was a very cost effective solution at £25/fan
compared with very large conventional silencers.
9-12
Top 10 Noise Control Techniques
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88
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Simple Ventilation Silencing
m85
Fan Outlet Silencer Cowl
steel / plywood
600 mm
ventilation silencer for
rooms of up to 150m^3
1000
mm
acoustic absorbent
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250
mm
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VC
acoustic absorbent
18swg steel sheet
duct
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150
mm
perforated sheet steel
25% open area c3mm
holes
Scrap Can Extract and Chopper Fans
A simple, cheap absorbent lined cowl can give a 10 - 20dB(A) noise
reduction in fan inlet /outlet noise
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Fan Speed v Noise
Problem
Occupational and environmental
tonal noise
BPM Engineering
internal fan modification reduced
tones by 23dB and overall noise
by 22dB(A)
Cost c £3000 - no maintenance
costs (lasts the lifetime of the
fans despite passage of cans)
sound
modified fan
speed reduction
noise reduction dB
10%
2
20%
5
30%
8
40%
11
50%
15
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Conventional
silencers, lagging and
enclosures
capital cost > c£35000 +
maintenance costs
Copyright 2009 INVC www.invc.co.uk 1753 698800
13-16
Top 10 Noise Control Techniques
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s85
Cooling Tower Silencer
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Boiler Burner
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16dB tonal noise reduction
w20
Sand Burner
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Noise Control - Best Practice
noise
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Pneumatics
Industrial Noise and Vibration Centre: Slough www.invc.co.uk
Copyright 2009 INVC www.invc.co.uk 1753 698800
17-20
Top 10 Noise Control Techniques
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Pneumatic Silencers
Pneumatic Nozzles
Entraining Nozzles
c10dB quieter for the same thrust
use c 20% less air
pay for themselves very quickly
intrinsically "safe"
reduce air pressure....
Silencer Solutions
zero back-pressure silencers - or a larger
coupling
standardise on 3 sizes
fix piped silencers to machine and
manifold multiple exhausts
entrained ambient air
annulus
directing cone
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compressed air
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m2
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Quiet Nozzle Design
Scrap Product Air-Lances
dB
100
95
90
85
80
0
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9
10
tool clearance (mm)
commercial nozzle
Cu pipe
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flatjet
Copyright 2009 INVC www.invc.co.uk 1753 698800
21-24
Top 10 Noise Control Techniques
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Filler Cooling Pipes
Noise Control - Best Practice
noise
Problem
94dB(A) from cooling pipes for
sealed tube ends - rapid cooling a
necessity
Conventional Solution
enclosure - high cost with hygiene
and productivity issues
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p10
Industrial Noise and Vibration Centre: Slough www.invc.co.uk
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Damping Thin Plates
unconstrained layer of
damping material
Vibration Damping
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BPM Solution
Coanda effect linear nozzles
12dB(A) noise reduction (82dB(A))
improved performance (less
turbulence disturbing tubes)
20% less air consumption - pay for
themselves very quickly
no effect on access or operation
s90
Vibratory Bottle Unscrambler
Problem
Vibratory feed hopper for
unscrambler generating 90dB(A)
damping material in
sandwich construction
damping material
BPM
poor design: vibrators at high
level to vibrate whole hopper feed still inefficient
sheet metal
laminated plate inside existing
hopper (grommet isolation),
connected to vibrators through
holes in hopper: cost c £400
damping material made to
shear over whole area
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damping material deforms
only near bends
Copyright 2009 INVC www.invc.co.uk 1753 698800
reduced vibrator level,
improved feed, noise reduced
from 90dB(A) down to 82dB(A)
25-28
Top 10 Noise Control Techniques
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m49
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Damped Dry Chiller
p1
115T Bliss Press
Dynamic vibration absorbers designed
and fitted to flywheel inside existing
guards.
10dB(A) noise reduction
£20 materials; 1 day fitter time
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Total 8dB(A) noise reduction under chiller (damping + absorbent)
Panel Vib
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Noise Control - Best Practice
n13
noise
Problem
High speed strip fed press at 101dB(A)
in a quiet area
Conventional
Manufacturer supplied "acoustic
guards" gave only 3dB(A) reduction.
Full enclosure suggested.
Industrial Noise and Vibration Centre: Slough www.invc.co.uk
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Vibration Isolation
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Verso Press
isolation pads
Copyright 2009 INVC www.invc.co.uk 1753 698800
BPM
Noise Control Audit showed
dominant source to be fabricated
press legs.
Tico isolation fitted between frame
and legs tuned to give natural
frequency of 65Hz for both legs
(different loads)
9dB(A) noise reduction at closest
operator position. £45 materials, 1
man day to fit
29-32
Top 10 Noise Control Techniques
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k58
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Hydraulic Power Pack
n10
Machine Foot Isolation
Looking at the diagnostic procedure for this power pack:-
load-spreading
steel washer
Tico
pad
m/c foot
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PPack
Tico
pad
bolt
EFFECTIVE
ISOLATION
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bolt
NO ISOLATION
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Noise Control - Best Practice
noise
Modify Existing Machine Guards
Minimise gaps
halving the open area of gaps in a set of guards will reduce the noise from
this source by 3dB
reduce the openings by 90% - 10dB noise reduction
Acoustic Absorbent
Line a significant proportion of the inside of guards with acoustic
absorbent (foam, rockwool)
Existing Guards
Guard vibration radiated as noise - use damping...
Industrial Noise and Vibration Centre: Slough www.invc.co.uk
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Test mock-ups
Copyright 2009 INVC www.invc.co.uk 1753 698800
33-36
Top 10 Noise Control Techniques
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Modify Existing Guards
"Blue Peter" Cardboard Engineering
gaps
open
outfeed
no acoustic
absorbent
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VC
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ringing box section
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VC
Noise Control - Best Practice
noise
Belt Drives
replace noisy chains with belts
use quiet tooth profiles on toothed
belts
chevron tooth pattern - ultra-quiet
replace wide belts with a pair of
narrower belts
Chains and Toothed
Belt Drives
toothed belt noise is very sensitive
to belt tension
Industrial Noise and Vibration Centre: Slough www.invc.co.uk
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5 - 20dB noise reductions possible
Copyright 2009 INVC www.invc.co.uk 1753 698800
37-40
Top 10 Noise Control Techniques
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Noise Control - Best Practice
noise
Buy Quiet Motors
Do not allow your suppliers to spend your money on noise control without close
scrutiny and evidence that they have followed diagnostic best practice
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Industrial Noise and Vibration Centre: Slough www.invc.co.uk
www.invc.co.uk
www.invc.co.uk
Buy Quiet Motors
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VC
Noise Control - Best Practice
Remote Control of Noise
noise
video
sound
photos
email
or CD
Remote Control
Industrial Noise and Vibration Centre: Slough www.invc.co.uk
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Specialised analysis
Free
evaluation of
noise control
costs and
options
Copyright 2009 INVC www.invc.co.uk 1753 698800
database
41-44
Top 10 Noise Control Techniques
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VC
Top 10 Noise Control Techniques...
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VC
.. + innovative "magic bullets" that may make you think...
noise
Low cost, DIY engineering best practice for common noise problems
fan installation details
simple ductwork silencing
fan speed
pneumatic exhausts
pneumatic nozzles
damping - chutes, hoppers, guards...
vibration isolation pads - motors, pumps...
upgrade existing guards
chains and toothed belts
quiet motors - buy quiet
Further information and case studies:
www.hse.gov.uk/noise
www.invc.co.uk
retro-fit fan modifications
Top 10
Noise Control
Techniques
yoghurt-based combustion
noise control
bolt-on quiet
free collateral quiet
www.invc.co.uk
www.invc.co.uk
1
2
3
4
5
6
7
8
9
10
Noise Control - Best Practice
Industrial Noise and Vibration Centre: Slough www.invc.co.uk
Copyright 2009 INVC www.invc.co.uk 1753 698800
45-48