PowerPoint PresentationSusham Biswas
Kanpur, 208016 INDIA
20th January , 2011
Sound Propagation Modeling at High Resolution Using LiDAR Data and Aerial Photograph for Outdoor environments
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Noise
map
Around
Airport
Animation
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Outdoor Sounds and its Relationship with Spatial and other Data : Modeling aspect
Indian Institute of Technology Kanpur
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Boundary Element Method
Directivity
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Direct Transmission
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How sound can reach receiver R from source PS
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Indian Institute of Technology Kanpur
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How sound can reach receiver R from source PS
Indian Institute of Technology Kanpur
Susham Biswas
Indian Institute of Technology Kanpur
Susham Biswas
*
In outdoor environment sound from a source follows one or many of the above paths before reaching to a receiver location thus the outdoor Sound propagation involves following spatial parameters
Distance between Source* (PS) and Receiver (R)
Path_difference for Diffraction
Possibility of Wall_reflection
* When there exists objects between Source and receiver the intermediate diffracting, reflecting points involved in transmission is termed as secondary source (SS) and original source as primary source (PS)
Spatial information required in sound modeling !!
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Spatial Input using
Contour
Accurate Comprehensive Surveying (time limitation)
Existing practices
Spatial Data
Low resolution satellite image/ aerial photo
Use of Total Station/GPS in limited scale
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Is there any Advantage of using high resolution spatial data?
Whether Better Data and/ or Model can lead to better prediction?
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Observed Sound
at outdoor
Prediction of Sound at Outdoor with Poor Data and Poor Model
Prediction of Sound at Outdoor with Good Data and Poor Model
Prediction of Sound at Outdoor with Good Data and Good Model
Comparison
Is there any Advantage of using high resolution spatial data?
Whether Better Data and/ or Model can lead to better prediction?
Can better data suggest ways of improvement in sound modeling?
Can LiDAR data & Aerial Photograph be used for Sound Modeling?
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Comparative Analysis
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Data Preparation
For Good data: Accurate Data e.g. from Total Station, or LiDAR and Aerial Photographic Survey etc
For Poor data: Errors added to good data
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Ground TIN
Ground type attribute
Classified aerial photo
How to do
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Indian Institute of Technology Kanpur
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Indian Institute of Technology Kanpur
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Cutting plane technique
Cutting plane orthogonal to X-Y plane and passing through source and receiver
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Intersecting points
Intersecting points with vertical line of intersection between buildings and cutting plane
Intersecting points & vertical line of intersection
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Finding effective intersecting points
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Determined principal path over top (i.e., PS-c-d-R)
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Cutting plane technique
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Intersecting points at cutting plane
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Determination of Principal Path due to diffraction (around sides)
Intersecting points and line of intersection between building side walls and cutting plane
Intersecting points & line of intersection
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Intersecting points and lines of intersection projected on XY plane
Intersection points with projected lines of intersection
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Principal paths around sides (i.e., PS-a-e-h-R and PS-b-c-R)
a
b
c
d
e
f
g
h
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Eight Principal path or routes between any pair of Source and Receiver
Source
Receiver
Source
Receiver
Source
Receiver
Source
Receiver
Source
Receiver
Source
Receiver
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Classified ground point
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Classified tree points
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Source
Receiver
The plane of “Wall”
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Dist S-R
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Gr. Type of ground reflecting point
Angles of reflections
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Gr. Type of ground reflecting point
Angles of reflections
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A transact (130mX 30 m) at IIT Kanpur Air strip containing building,
different ground types, tree, is used to monitor SPL and validate that with developed model
Validation experiment
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Measured
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Experimental Detail- Sound Measurement (at receiver)
Sound Measured simultaneously at a fixed position at source as well
Experi-mental Site
Parameter studied
Metero-logical Condition
130mX 30m, At Air Strip, having building and different ground types
SPL
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Predicted SPL in dB (for Good data and Good Model1)
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Deviation
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Deviation
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Deviation
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Deviation
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Mean and SD
Tukey Test
Error Propagation
Intradata analysis for the best prediction scheme of the above three
Data Processing and Data Analysis
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Statistical Analysis
500
8.46
7.11
34.02
0.03
1000
8.35
7.35
41.99
0.04
4000
9.59
8.75
42.00
0.03
 
 
 
 
 
 
 
 
500
9.22
8.32
39.55
0.00
1000
9.09
8.46
44.94
0.07
4000
10.86
9.39
44.94
0.03
 
 
 
 
 
 
 
 
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ANOVA statistical test for four prediction schemes
At least one of the four prediction schemes giving different results
Statistical Analysis
Abbreviations used
Comparison of Deviation
Probability of H0 to be true at 0.05 significance level
250 Hz
1.11*10-16
500 Hz
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Statistical Analysis
Comparison of different pairs of prediction schemes in terms of deviation
t(0.05,120)=1.645
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Hence, generally the prediction scheme involving Good Data & Good Model1(Coherent) seems to performed the best
Analysis
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Study area: part of academic area of IIT Kanpur. Buildings are shown with red and ground with blue
SPL (in dB) at different locations due to distance attenuations
SPL (in dB) at different locations due to ground attenuations
Stages of sound prediction over LiDAR data points
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SPL (in dB) at different locations due to barrier attenuations
SPL (in dB) at different locations due to distance + barrier attenuations
Binary plot of probable reflecting and non-reflecting points
Stages of sound prediction over LiDAR data points
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*
Sound propagating from a single source to nearby points in 3D
Sound map developed by incorporating LiDAR data/Google Earth Image of IIT Kanpur inside sound model
Representation of Sound
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Audio Realization
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Discussion and Conclusion
LiDAR/Aerial Photo data can be use to incorporate detail terrain information for outdoor sound propagation modeling
In general Good data and Good Modeling (complex coherent) scheme is giving the best results which answers the research question whether better data and model can lead to better results.
Present study indicates the technique to determine principal paths of propagation even for complex terrain
Indian Institute of Technology Kanpur
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*
In indicates techniques to incorporate accurate spatial parameters such as path- difference, ground type, angle of reflection, barrier shape etc which were not been possible previously for real outdoor sound modeling.
It can be used for 3D sound mapping rather than conventional 2D mapping
It can generate higher resolution sound map/sound contour
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D. A. Bies and C.H. Hansen. Engineering Noise Control., Theory and practices Unwin Hyman (2003)
"The Propagation of Noise from Petroleum and Petrochemical Complexes to Neighbouring Communities". CONCAWE Report 4/18, (1981).
ISO 9613-2, 1996(E), ‘Acoustics-Attenuation of sound during propagation outdoor-Part 2: General method of calculation’, p.1-18.
Maekawa, Z 1968, ‘Noise reduction by screens’, Applied Acoustics, 1, p. 157–173.
RTA group (n.d.),ENM-Environmental Noise Model-Program Specification, viewed 7 December, 2007
<http://www.rtagroup.com.au/enm/environmental_noise_model.html>.
Renzo Tonin 2004, Modeling and Predicting Environmental Noise, viewed 12 November 2006, < http://www.rtagroup.com.au/pdfs/22.pdf >.
Soundscape, further reading, viewed 7 september 2007, http://en.wikipedia.org/wiki/Soundscape#Further_reading
Important References
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Coherent Addition of two 40dB Tonal Sounds at Diff. Phase Difference
Simulations to assist theoretical understanding and research findings
Phase Difference in deg.
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Simulations to assist theoretical understanding and research findings
SPLcombined_40_40=43.01 dB 1
Effect of Background Noise
SPLcombined_80_40=80.0004 dB
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Simulations to assist theoretical understanding and research findings
How different frequency sounds are affected by same geometry
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Low Frequency wave (higher wavelength)
Spatial distribution of Interference maxima
Wavelengths of 4 tonal sounds used
250Hz1.36 m
500Hz0.68 m
1000Hz0.34 m
4000Hz0.085 m
Interference and Frequency
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Path_difference=2.36 m
Why at shorter distance prediction is more dependent on accurate data
50 m
50 m
Path_difference=0.49m
5 m
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Determination of Principal Path for over top of buildings –after points of intersection and vertical lines of intersection are determined
( It tries to determine path from PS to R via secondary source(s) (SS))
Straight line is drawn between PS and R , if PS-R line is not been intersected by any line of intersection Direct transmission else
All the intersecting point/line below PS-R are eliminated (if any)
Straight line is made between PS and tallest intersecting point, if this line is not been intersected by any line of intersection then tallest intersecting point becomes a secondary source (SS). And iteration continues from SS as above till sound reaches the receiver.
If this line is being intersected then, tallest amongst them becomes the SS .And iteration continues from SS as above till sound reaches the receiver.
Indian Institute of Technology Kanpur
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*
Determination of Principal Paths around sides of the buildings –after points of intersection and lines of intersection at side walls are determined
( It tries to determine path from PS to R via secondary source(s) (SS))
Line is drawn between PS to R , all lines of intersection not intersected by this line will be deleted for the current iteration. Rest of the intersecting points along with lines of intersection will be tested for finding SS
Among the available lines of intersections nearest one from PS is chosen first. Two intersecting points attached to it becomes the first pair of SS
From each of the above SS iteration continues seperately
Straight line is drawn between SS to S and checked for finding intersecting ‘lines of intersection’. When there is no such line or only one line belonging to same building then there is no further SS in the principal path. When there are two or more such line but all belonging to same building from which the iteration is being tested then the next SS belongs to same building. When there are two or more such line but belonging to same or different building then, it tries to select intersecting point(s) attached to nearest ‘line of intersection’ of either building maintaining criteria of shortest route to reach R.
Step 4 repeats iteratively till sound reaches to R
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