Vibration and Noise

• Sources of vibration & noise
  • Engine, transmission, and exhaust
  • Road and wheels
  • Wind

• Effects of vibration and noise
  • Comfort
  • Handling, stability, and control
  • Wear and tear on vehicle

• Measure of vibration
  • Frequency (f)
  • Measured in Hz (cycles per second)

• Measure of noise
  • Decibel (db)
  • e.g., if sound A is 2 bels more powerful than sound B, then A is 10² times louder

   

• Natural frequency (or, resonance frequency)

  • The frequency at which an object resonates

• The challenge is to design the vehicle such that its natural frequency is not similar to the frequency of the sources of vibration

• Ideally, a vehicle’s torsional and bending stiffness should allow it to have a natural frequency of 20-30 Hz

Modes of vibration

• Vibration of suspension system and wheels
• 5 - 10 Hz

• Caused by engine shake
• 11 - 17 Hz

• Vibration of the body
• 25 - 40 Hz

• Passenger compartment and the bending vibration of the driveline
• 50 - 150 Hz

• Resonance of the cavity space in the passenger compartment
• 90 - 150 Hz

Effects of Vibration on Occupant

• 0-5 Hz Normal ride
• 5-25 Hz Shake
• 25-200 Hz Harshness

• Some people experience motion sickness with vibrations close to 4 Hz

Body Design and Noise

• Body structures’ rigidity must be controlled
• Example, pillar bonding rigidity
  • Addition of pillar outer panel reinforcements between each pillar at appropriate structures
    • Roof side rails
    • Windshield header
    • Rocker panel
    • Quarter panel extensions

Noise Analysis

Noise pressure can be obtained and analyzed via FEM/FEA

Body Design and Noise

Wind Noise

Controlling Wind Noise

• TEC452 Home
• Body Engineering Index
• Body Components
• Body Design Factors
• Unitized B-I-W
• Hydroforming
• Vibration and Noise
• High-Strength Steel Design Guidelines
• Glass Design
• Neon B-I-W Case Study