# Presentation: 535556

## Research on Health Risk due to Impulsive Noise and Vibrations 

- Research Results Conducted in Collaboration with NIOSH
- 		Professor Jay Kim
- 		Students:
- 			Xiangdong Zhu, Wonjoon Song
- 		University of Cincinnati
- 		March 2006

## 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

## 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

- Measured noise from power wrench

## 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.

## 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

## 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

## Analytic Wavelet Transform (AWT): brief background (1/2)

- Use variable time-frequency atom: source of the main advantage of wavelet analysis for transient signals

**Problems**
- Works in un-familiar terms to engineers and scientists:  scale, wavelet intensity, etc. instead of frequency and amplitude

## 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

- Our version of AWT is set up so that each AWT provides a time history of 1/3 octave component of center frequency of

## AWT: application example(1/2)

- 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

## AWT: application example(2/2)

- Airbag sound

- T-F plot

- 1/3 octave time histories

## 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

- AWT

- T-F noise metrics

- Statistical correlation study to choose the best metric

- Chinchilla NIHL model

**Human NIHL model**

**Existing data**

- Proposed research

## 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

## 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 data

- Repeat NIHL model development for cats using cat experiment data

- Confirm scaling law

- development

- use

- Compare to validate

## Example of Ear Model: AHAAH model developed 		by Price and Kalb

## Hand Arm Vibration Syndrome (1/3)

- Time series

- T-F representation with ISO HA frequency weighting

- T-F representation with one of frequency weightings proposed for fingers

## Hand Arm Vibration Syndrome (2/3)

- Sum frequency components at each time point

- Frequency weighted time history: reflects what hand arm feel

## Hand Arm Vibration Syndrome (3/3)

- Non-linear metric function

- Threshold level

##  Gunshot sound analysis 

- Outside of ear protector

- Inside of ear protector

- Reduce SPL

## 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  **

## Questions/Suggestions?