1. Acoustic Signature for Automotive
Seat Rattle
Tuan Quach,
Joseph Hasna,
Khai Win Er,
Wenhao Li
School of Aerospace, Mechanical and Manufacturing Engineering
Supervisors:
Dr. M. Fard (RMIT)
Tony Baxter (FUTURIS)

2. Introduction
5/7/2015 Acoustic Signature for Automotive Seat Rattle 2
Why is it important to investigate NVH?
• Characteristics of noise and vibration are important factors in terms
of design quality and build for mechanical systems.
• Vital to a vehicle’s success that noise and vibration be reduced as
much as possible.
• Automotive seat rattle is particularly important as there is direct
interaction between passenger and the seat.
• In order to mitigate noise and vibration, the sources must be
identified.

3. Project Objective
5/7/2015 Acoustic Signature for Automotive Seat Rattle 3
Main Objectives
• Analyse seat structural behaviour and sound characteristics.
• Characterise rattle behaviour to locate noise sources.
• Provide recommendations to diagnose rattle prior to design phase.
RESEARCH EXPERIMENT VALIDATE RECOMMENDATIONS
Characterising
rattle
Experimental
Process
Correlate &
Validate
Managing rattle
NVH – Seat Rattle
Optimization of
experiment
Rattle Noise
Database

4. Importance of Research
5/7/2015 Acoustic Signature for Automotive Seat Rattle 4
Why focus on Seat Rattle noises?
• Seat serves as a final link for vibrational sources.
• Overall vehicle satisfaction directly correlates to interior quietness
RatingofOverallVehicleQuality
Rating of Overall Interior Quietness
Overall vehicle satisfaction

5. Importance of Research
5/7/2015 Acoustic Signature for Automotive Seat Rattle 5
Why focus on Seat Rattle noises?
• Resonance can lead to violent vibration
• Constant resonant noises can be hazardous to concentration

6. Methodology
5/7/2015 Acoustic Signature for Automotive Seat Rattle 6
Modal Analysis Testing
To determine the resonance
frequencies of the seat along with
its respective mode shapes.
Acoustic Camera
Testing
Recommendation

7. Results
5/7/2015 Acoustic Signature for Automotive Seat Rattle 7
g.N
Amplitude
250e-3
Lateral Mode
8.65 Hz
Twisting Mode 2
37.16 Hz
Twisting Mode 1
22.88 Hz
Bounce Mode
16.97 Hz

8. Methodology
5/7/2015 Acoustic Signature for Automotive Seat Rattle 8
Acoustic Camera Testing
To pin-point the source of the rattle
noise at its respective resonance
frequencies.
Modal Analysis
Testing
Recommendation

9. Results
5/7/2015 Acoustic Signature for Automotive Seat Rattle 9
Lateral Mode- 8.65 Hz
Twisting Mode 2- 37.16 HzTwisting Mode 1- 22.88 Hz
Bounce Mode- 16.97 Hz

10. Results Refinement
5/7/2015 Acoustic Signature for Automotive Seat Rattle 10
• Some spectrogram shows unclear
results due to noise from
the overall seat.
• Refinement of the excitation range
would pin-point the main source
of noise (rattle).

11. Conclusion
5/7/2015 Acoustic Signature for Automotive Seat Rattle 11
• Controlling of rattle in early design phase is challenging and industry is still
using find & fix for rattle.
• Strong correlation has been found between seat structure dynamics and
rattle noise (structural vibration modes).
• Management of the three main seat vibration modes in early design phase
can significantly reduce time and cost.
• Experiments revealed resonant frequencies at 8.65Hz, 16.97Hz, 22.88Hz
and 37.16Hz.

12. Recommendation
5/7/2015 Acoustic Signature for Automotive Seat Rattle 12
Altering the natural frequency of the seat
• Resonance occurs when the input frequency is the same as the natural
frequency of the seat.
• Vibration sources such as engine’s combustion usually vibrate below 30Hz.
• By shifting the natural frequency to a higher frequency, resonance could
possibly be avoided.
• This could be done by changing the material properties of the seat (stiffness
and mass).
Natural Frequency =
𝑆𝑡𝑖𝑓𝑓𝑛𝑒𝑠𝑠
𝑚𝑎𝑠𝑠

13. Recommendation
5/7/2015 Acoustic Signature for Automotive Seat Rattle 13
Minimize the impacting surface area
• From the results, it was found that most of the noises come from
connection points.
• By minimizing the impacting surface area, it could restrict the movement at
the connection points, therefore further reduce the sound emitted.
• This could be by changing the direction of the pin at the point of interest.
Mode Recommendation
Lateral Mode 8.65 Hz
Restriction in the
horizontal direction
Restriction in the vertical
directionBounce Mode 16.97 Hz

14. 5/7/2015 Acoustic Signature for Automotive Seat Rattle 14
Thank you.
Questions