Research on Health Risk due to Impulsive Noise and Vibrations
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Transcript of Research on Health Risk due to Impulsive Noise and Vibrations
University of CincinnatiApplied Acoustics/Mechanics Lab
Research on Health Risk due to Impulsive Noise and Vibrations
Research Results Conducted in Collaboration with NIOSHProfessor Jay KimStudents:
Xiangdong Zhu, Wonjoon SongUniversity of CincinnatiMarch 2006
University of CincinnatiApplied Acoustics/Mechanics Lab
Presentation Overview
Background Analytic Wavelet Transform as the Basic Signal Analysis
Tool for Impulsive Events Hearing Loss Due to Impulsive Sound
Current work Long-term approach
Hand Arm Vibration Syndrome (HAVS) Some preliminary results Planned approach
Other Applications of AWT Gunshot data/ear protector analysis AWT based rotating systems analysis
University of CincinnatiApplied Acoustics/Mechanics Lab
Background: Conducting NIOSH-UC power tool research consortium, lack of method for assessment of exposure risk to impulsive noise and vibrations
Impulsive Noise Induced Hearing Loss (INIHL) Complex noise environment in
workplaces Military noises
Hand-Arm Vibration Syndrome (HAVS) due to impulsive vibrations
Current codes are based on steady-state metrics ignoring temporal variation of spectral characteristics
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Impact Wrench
Measured noise from power wrench
University of CincinnatiApplied Acoustics/Mechanics Lab
Issues in Risk Assessment of Impulsive Noise and Vibrations Inherent difficulties of transient events
More parameters are necessary to characterize the event Difficult to formulate metric and relate it to experimental or
demographic study results Characterization technique: time-frequency analysis is
necessary Wavelet analysis should be a choice, but nearly entire existing
practices and data are based on Fourier quantities Analytic Wavelet Transform (AWT): a hybrid of wavelet and FFT
that works like a superb transient FFT analysis. All Fourier definitions, SPL, frequency spectra, can be defined in transient sense.
University of CincinnatiApplied Acoustics/Mechanics Lab
Current Status (1/2): Impulsive Noise
Impulsive Noise: Current standards (OSHA, NIOSH, European standards) are
based on equal energy hypothesis (85 dB, 6 dB exchange rule) Use of dBA is considering spectral information Temporal information is considered in very limited sense through
allowable maximum peak SPL Temporal variation of frequency spectrum is not considered
Research efforts to reflect temporal variations: AHAAH model by Price and Kalb: time domain simulation of human
ear Chinchilla based study on INIHL by Hamernik et. al.
Expose chinchillas to steady-state and impulsive/complex noise Used Kurtosis as the metric to represent temporal variations
University of CincinnatiApplied Acoustics/Mechanics Lab
Current Status (2/2): Impulsive Vibrations
Impulsive Vibrations: Similar to INIHL cases because of the transient nature, but
dissimilar because hand and arm do not have spatial frequency sensor as the hearing organ
Group of researchers at NIOSH Morgantown Established frequency weightings for hand-arm vibrations and finger
vibrations Developed standard test procedures, numerical models,
demographic study and theoretical background Collaboration with UC is embarked in applying AWT and transient
analysis technique to HAVS
University of CincinnatiApplied Acoustics/Mechanics Lab
Analytic Wavelet Transform (AWT): brief background (1/2)
Use variable time-frequency atom: source of the main advantage of wavelet analysis for transient signals
tu
s
os
ou
,u s ,o ou s
,ˆ ( )o ou s
,ˆ ( )u s
os
s
/ os
/ s
picks up fast, high-frequency components
picks up slow, low-frequency components
Problems
Works in un-familiar terms to engineers and scientists: scale, wavelet intensity, etc. instead of frequency and amplitude
University of CincinnatiApplied Acoustics/Mechanics Lab
Analytic Wavelet Transform (AWT): brief background (2/2)
Hybrid of wavelet transform and Fourier transform Work in terms of traditional Fourier variables: frequency, amplitude
and phase, however all as functions of time A perfect replacement of Short-time Fourier transform (STFT) for
transient analysis
*, ,( ) ( ), ( )s t s t sW t f u f u dt
,
1( )u s
u tu
s s
2
222 1/ 4
1( ) ( )
( )
tj t j tt g t e e e
Our version of AWT is set up so that each AWT provides a time history of 1/3 octave component of center frequency of
s
University of CincinnatiApplied Acoustics/Mechanics Lab
AWT: application example(1/2)
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Impact Wrench
Impulsive sound, time domain
T-F representation by AWT with cochlea mapping T-F representation by STFT
Inst. 1/3 octave spectrum
1/3 octave time history
Superiority of AWT compare to STFT is clear
AWT
STFT
University of CincinnatiApplied Acoustics/Mechanics Lab
AWT: application example(2/2)
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dBA
, 12
5 H
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time, s0 0.05 0.1 0.15 0.2
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dBA
, 12
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z
time, s
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dBA
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time, s0 0.05 0.1 0.15 0.2
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dBA
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00 H
z
time, s
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dBA
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00 H
z
time, s0 0.05 0.1 0.15 0.2
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dBA
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time, s
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Airbag sound
T-F plot
1/3 octave time histories
University of CincinnatiApplied Acoustics/Mechanics Lab
Hearing Loss due to Impulsive Sound (1/3): Current approach in pending NIH proposal
Chinchilla Test Data at SUNY-Plattsburgh
Digitized Noise data
Various, controlled noise set
About 400 Chinchillas
TTS, PTS, IHC and OHC loss data as functions of frequency
AWTT-F noise metrics
Statistical correlation study to choose the best metric
Chinchilla NIHL model
Human NIHL model
Existing data
Proposed research
University of CincinnatiApplied Acoustics/Mechanics Lab
Hearing Loss due to Impulsive Sound (2/3): long-term plan
Human NIHL model
Chinchilla ear model
Human ear model
Ear simulation model output (basilar membrane displacement)
Ear simulation model output
Inter-species scaling law
Environmental Noise AWT
NIHL risk
noise metric
Final form of implementation
Necessary development
University of CincinnatiApplied Acoustics/Mechanics Lab
Hearing Loss Due to Impulsive Sound: long-term plan (3/3): Develop inter-species scaling law
Chinchilla NIHL model
Simulation ear model for chinchillas
Test Noise Data
Cat NIHL model
Simulation ear model for cats
Model output (basilar membrane displacement)
Model output
Inter-species scaling law
Simulated cat NIHL dataRepeat NIHL model
development for cats using cat experiment data Confirm scaling law
development
use
Compare to validate
University of CincinnatiApplied Acoustics/Mechanics Lab
Example of Ear Model: AHAAH model developed by Price and Kalb
Outer EarInner Ear
Middle Ear
area
Ue
Pe Lh RhCb
LdsCds
Rds
Eardrum conductive part
Ldm Cdc Rdc 1:Nt
Cm
Diffraction sound field
Air Plug
ConchaEarcanal
Li Ls Cal Ral LvCochleaIncus Stapes
Annular ligament
Vestibular Volume
Uc
Lo
RoRcPc
HelicotremaRound window
Incudo- stapedal
joint
Malteo- Incudal
joint
Lever and area
ratio
Eardrum independent
partBulla
Rmi
Cmi Cis
Ris Crw
Rdf
Ldf
2P P
Lpl
Rpl L1 L2 L3
A1 A2 A3
length
University of CincinnatiApplied Acoustics/Mechanics Lab
Hand Arm Vibration Syndrome (1/3)
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x-di
r ac
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n [m
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x-di
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Time series
T-F representation with ISO HA frequency weighting
T-F representation with one of frequency weightings proposed for fingers
University of CincinnatiApplied Acoustics/Mechanics Lab
Hand Arm Vibration Syndrome (2/3)
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time [sec]
tota
l acc
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n [m
/s2 ]
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time [sec]
tota
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( ) ( , )fn
f f ii
a t A f t
Sum frequency components at each time point
Frequency weighted time history: reflects what hand arm feel
University of CincinnatiApplied Acoustics/Mechanics Lab
Hand Arm Vibration Syndrome (3/3)
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HAVS threshold acceleration level
Metric based on frequency weighted time history
Hazard dose curve
2
11 1
( )1 1N Nf j th
jj j th
a t aI I
N N a
( )
21 1
1 1 1f j th
th
a t aN N
j aj j
eI I
N N e
Non-linear metric function
Threshold level
University of CincinnatiApplied Acoustics/Mechanics Lab
Gunshot sound analysis
Outside of ear protector
Inside of ear protector
Reduce SPL
University of CincinnatiApplied Acoustics/Mechanics Lab
Other Interesting Application: AWT based Campbell diagram
Fourier transform based Campbell Diagram
AWT based Campbell Diagram
Rotating system start-up analysis
In-situ FRF construction without excitation
University of CincinnatiApplied Acoustics/Mechanics Lab
Questions/Suggestions?