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ACOUSTIC CHARACTERISATION OF LAMINATED
GLASS FOR SUPERYACHTS WINDOWS
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19 RO-RO Transport Passenger
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17 Pleasure Vessel
25 Pleasure Yacht
12 Oil Chemical Tanker
10 Supply Vessel
1 Escort Tug
3 Sailing Vessel (catamaran, sloop).
Additional voluntary notation: when
full-scale measurements verify that noise
and vibration limit levels are respected, the
additional class notations for comfort on
board can in turn be assigned as follows:
COMF Yacht to assess the noise and
vibration levels on pleasure or charter
yacht
Comfort Class
COMF (X,Y)
X: merit parameter of noise levels (100 lowest level of noise)
Y: merit parameters of vibration levels (100 lowest level of vibration)
All notations are given after the on board measurements comparison with the limit levels for cruising condition and at berth
The notation is:
the same for all pleasure and charter yacht
Different limit for type of spaces on planning and displacement boats
Only assigned if at least both merit level are larger than 30
Comfort Class Pleasure Yacht – “COMF (Y) (X,Y)”
LOCAL YACHT Navigation At berth
Lmin [dB(A)] Lmax [dB(A)] Lmin [dB(A)] Lmax [dB(A)]
Operation
compartment All 55 65 40 50
Public spaces
(closed) All 60 75 40 50
Public spaces
(open
recreational
areas)
Semi-planning or
planning - - 50 60
Displacing 65 75 50 60
Passengers’
cabins
Semi-planning or
planning - - 40 50
Displacing 50 60 40 50
TABLE NOISE LIMITS
COMFORT for Yacht Limit levels 1/2
TABLE VIBRATION LIMITS
LOCAL YACHT Navigation At berth
Vmin[mm/s] Vmax[mm/s] Vmin [mm/s] Vmax [mm/s]
Operation
compartment All 2 5 2 4
Public spaces (closed) All 2 5 1 3
Public spaces
(open Recreational
areas)
Semi-planning
or planning - - 2 4
Displacing 2 5 2 4
Passengers’ cabins
Semi-planning
or planning - - 1 3
Displacing 1 4 1 3
R’w limits Loa>24m =
45 between passenger cabins and machinery or auxiliaries rooms
30 for walls between passenger cabin
No Impact Noise Insulation are required
COMFORT for Yacht Limit levels 2/2
L. Gragnani, D Boote and T Pais, University of Genoa
A. Tonelli, RINA SERVICES S.p.A, Genoa
ACOUSTIC CHARACTERISATION OF LAMINATED GLASS FOR SUPERYACHTS WINDOWS
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
The ACOUSTIC COMFORT is nowadays a fundamental parameter in the superyacht design process
SOUND PRESSURE LEVEL:
Noise
sources
on board:
All of these
sources may
transmit their
vibration energy
as:
structure borne noise
(SBN)
airborne
noise
(ABN)
air pressure logarithmic increment compared to the air rest condition
main and auxiliary engines
gears
exhaust systems
propellers and thrusters
air-conditioning units
…
In this framework, the current trend in pleasure yacht
of using larger and larger glass windows, especially for
owner and vip's cabins, could lead to the occurrence of
serious noise and vibration problems
• Material used:
• Installation
technique:
Laminated glass
The window is clamped and
glued on the surrounding metal
structure
INTRODUCTION
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
Graphs highlight a dominant tone at low frequencies that is
related to the firing frequency of the engine ( ≈ 110Hz).
Accelerometer
CASE STUDY
noise and vibration level in the
owner’s cabin during a 16kn sailing.
Measurement under
consideration
47 m length superyacht on which an extensive measurement campaign of noise and
vibrations has been carried out (data kindly provided by RINA Service).
the main radiated panel is a 1635x815mm
flat laminated glass windows
Microphone Sonogram
Sonogram
Pure Tone
Graph
Pure
Tone
Graph
INTRODUCTION
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
To identify a method for the dynamic characterization of laminated glass AIM OF THIS
WORK
APPLICATION
to identify the FE model for obtaining results with a proper
level of accuracy avoiding high computational times.
Preliminary
static analysis
Dynamic
analysis
Experimental
analysis Reverberation Time
test
Numerical analysis
for identifying a dynamic model of laminated glass that
matches as accurately as possible the real structure
acoustic behaviour and that is able to take into account
the polymeric interlayer viscoelastic effects
Experimental modal analysis
METHOD
Statistical Energy Analysis of a 52m superyacht whose owner’s cabin has
three large laminated glass windows
INTRODUCTION
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
Register Monolithic glass:
minimum thickness
Laminated glass:
equivalent thickness
RINA
LLOYD’S REGISTER
ABS --
0,50
0,55
0,60
0,65
0,70
0,75
0,80
0,85
0,90
0,95
1,00
0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 0,45 0,50
percentage of ttot
t2 as a percentage of ttot
Equivalent thickness of laminated
glass as a percentage of ttot
where:
• b=s length of the shorter side of the window;
• β e k coefficient depending on window
aspect ratio;
• p design pressure;
• σa 30% of the material flexural strength.
The regulations considered in this study for the scantling of laminated glass windows are those proposed by
RINA, Lloyd’s Register and American Bureau of Shipping.
Is it better to use
symmetric or
asymmetric laminated
glass structures?
Looking at RINA and Lloyd’s Register
formulas:
the more different
the thicknesses of
the two layers are,
the higher the
equivalent
thickness will be
REGULATIONS: STATE OF THE ART
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
laminated glass is an assembly consisting of one sheet of glass with one or
more sheets of glass joined together with one or more interlayers.
CNR definition of
laminated glass:
Constitutive components:
1. Glass Density ρ 2250 - 2750 kg/m3
Young Modulus E 63000 - 77000 MPa
Poisson ratio ν 0.20 - 0.24
linear elastic
behaviour
• level a:
2. Viscoelastic
interlayer
polyvinyl butyral
(PVB) Its behaviour is
affected by
temperature
time
load
modelling
levels:
• level b: linear elastic model with constant elastic parameters
• level c: linear viscoelastic model
• level d: nonlinear models
Enhanced Effective Thickness
Method (EET) model with effective
monolithic thickness
LAMINATED GLASS
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
200 N
FEM models:
• “BRICK” model
• “SHELL” model
• “BRICK - SHELL - BRICK” model
• “SHELL - BRICK – SHELL” model
Structure under investigation:
t1 = t2 = 3.9 mm
tPVB = 0.76 mm
Buondary condition:
four side supports
Inapplicability of
the classical
laminated plate
theory
RESULTS
Element types
• 5 types of hex 8
• 2 types of hex 20
PVB modelling level:
• Linear elastic
model:
E = 2.36 MPa
υ = 0.45
ρ = 1070 kg/m3
Brick-shell-brick model Shell model - composite
MSC Nastran
STATIC ANALYSIS
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
SAMPLES sample 1 sample 2 sample 3
Dimensions [mm]x[mm] 300x300 300x300 300x300
Total thickness [mm] 16.38 6.38 13.52
Glass plies
thickness [mm] 8 3 6
PVB thickness [mm] 0.38 0.38 1.52
TEST 1
Test set up Natural frequencies extraction Mode shapes identification
EXPERIMENTAL MODAL ANALYSIS
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
TEST 2:
Accelerometer signal
Coherence
FRF
Amplitude and
phase
Nyquist plot Real and imaginary part
Hammer impulse
EXPERIMENTAL MODAL ANALYSIS
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
-1
-0,5
0
0,5
1
0,005 0,007 0,009 0,011 0,013 0,015
time [s]
MODE 1 Damping loss factor η
sample
n°
fR
[Hz]
hal power
band width
circle
fit
logarithmic
decrement RT60
1 1000 0.100 0.103 0.106 0.110
2 400 0.061 0.060 0.111 0.061
3 800 0.125 0.130 0.126 0.092
3) Logarithmic Decrement Method
2) Circle Fit Method
1) Half Power Bandwidht Method 4) Reverberetion time
test
Results:
RT60
Method
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0,4
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
[ Hz ]
xn xn+m
EXPERIMENTAL MEASURE OF DAMPING
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
100
200
300
400
500
600
700
800
900
1000
1100
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1
f31 [Hz]
η2D
Equivalent
flexural
stiffness
Equivalent
thickness
1) 3D FEM model
calibration sensibility study of natural frequencies on PVB elastic modulus
2) Identification of the coupling coefficient η2D
and the equivalent monolithic thickness by
EET method
sample 1
sample 2
sample 3
Sample 1
Natural mode 1 2 3 4 5 6
Percentage error 3D - analytical 4% 8% 0% -4% -4% -11%
Percentage error 2D - analytical 5% 6% 0% 3% 3% 1%
Percentage error 2D – 3D 1% -2% 0% 7% 7% 11%
3) Creation of
the 3D FEM
model
• monolithic
glass
• free sliding
plies limit
cases:
• Sample 1 :
• Sample 2 :
• Sample 3 :
teq = 15.23 mm
teq = 5.9 mm
teq = 12.12 mm
(ttot = 16.38 mm)
(ttot = 6.38 mm)
(ttot = 13.52 mm)
NUMERICAL ANALYSIS ON SAMPLES
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
35sb, 36sb, 37sb Dimensions
lenght width width of adhesive
perimeter
mm mm mm
1264 1380 50
layer n° composition thickness
mm
1 glass 8
2 PVB 0.38
3 glass 8
120
140
160
180
200
0 100 200 300 400 500 600 700
dB ref=1
Hz
2) Identification of the frequency at which the
panel radiates more noise into the cabin cavity
with the Equivalent Radiated Power method
(fluid-structure interaction approach)
3) Modal density computation
0,0010
0,0100
0,1000
10 100 1000 10000
mode/ (rad/s)
Hz
modal density - FEM
modal density - SEA1) Deterministic study to identify the dynamic
properties of the laminated glass panels
(structural approach)
The vessel under consideration is a 52m superyacht.
Critical point:
Owner’s cabin
3 large windows made of
laminated glass (35sb, 36sb, 37sb)
located above the engine room
CASE STUDY
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
“Statistical emphasizes that the systems being studied are
presumed to be drawn from statistical populations having
known distributions of their dynamical parameters.
Richard F. Lyon,
Statistical Energy Analysis of dynamical
systems: theory and applications
Energy denotes the primary variable of interest. Other
dynamical variables such as displacement, pressure, etc., are
found from the energy of vibration.
The term Analysis is used to emphasize that SEA is a
framework of study, rather than a particular technique.”
Frequency range
of application
It is a well established method for the acoustic calculation in aeronautic and automotive fields
Still developing in the naval field additional
problems high power involved
contribution of sea water in the sound transmission
high comfort requirements onboard
Main steps of the construction of the SEA model of a yacht:
STATISTICAL ENERGY ANALYSIS
• modelling the yacht in terms of the fundamental SEA subsystems, i.e. beams, plates and acoustic cavities;
• assignment of properties and noise control treatments to subsystems;
• introduction of a Semi-Infinite Fluid (SIF) to take into account the presence of sea water around the hull;
• application of the noise sources.
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
20
30
40
50
60
10 100 1.000 10.000
TL
dB
Hz
power inputs - owner’s cabin dB(A) ref =1e-12 W
2 layers 3 layers
window 35 sb F 39.1 36.7
window 36 sb F 39.1 35.8
window 37 sb F 39.1 36.2
Comparison between the noise contribution of a
2 layered glass and a 3 layered glass
Transmission Loss of windows
Overall sound pressure level
-100
-80
-60
-40
-20
0
20
40
60
10 100 1.000 10.000
dB(A) ref=1e-12W
Hz
Power inputs – owner’s cabin
total fin 36 ps F fin 37 sb F
fin 35 ps F fin 35 sb F fin 37 ps F
fin 36 sb F
STATISTICAL ENERGY ANALYSIS
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
common composite material in the construction of
yacht windows
very complex behaviour, due to its
composition
it is important to verify the contribution of such laminated glass structures to noise
radiation onboard
1) Definition of the acoustic properties of laminated glass using
natural frequencies and mode shapes, damping loss factor and
equivalent radiated power (ERP) by experimental test on
representative specimens
LAMINATED
GLASS
Our
investigation
focused on:
3) Calculation of the Sound Pressure Levels in the cavity with glass
on the boundary with SEA model
2) Extension of the specimens results to the real size by FEM
calculation and definition of the equivalent dynamic properties in
the SEA model
CONCLUSIONS
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
Thank you for your attention
RINA SERVICES S.p.A.
Via Corsica, 12
16128 Genoa - Italy
Ph. +39 010 53851
Fax +39 010 5351000
www.rina.org
UNIVERSITÀ
DEGLI STUDI
DI GENOVA
