Acoustic Characteristics of Automotive Damper during Fluid Structure and Structural Interactions

Acoustic characteristics of hydraulic dampers used in passenger cars are investigated. Experimentation work is carried out with servo hydraulic machine. Semi-anechoic chamber is used to isolate damper in order to study noise source in damper. Noise and vibration data analysis is performed with the help of OROS software. OROS provides noise and vibration testing solution. This is specifically used here for noise and vibration data acquisition and analysis for damper. Noise and vibration tests are performed by various frequencies and amplitude excitation inputs given to damper. As a part of low to mid frequency excitation, the amplitude of damper excitation is 20 mm in rebound and 10 mm in compression stroke of damper with data containing multiple input frequencies namely 0.5, 1, 1.5 and 2 Hz. This test condition ensured that the noise is perceived to car cabin by means of damper rather than filtration unit attached to damper. As a part of high frequency excitation, damper is stroked at low amplitude and high frequency typically ±5 mm in rebound and compression stroke of damper, respectively where 5, 10 and 12Hz are the input frequencies taken for understanding the rattling noise. This test condition ensured that noise transfers from the damper to vehicle cabin by means of filtration unit or top mount assembled in damper. During these test conditions, damper behaves nonlinearly under various input frequencies. The characteristics of annoying components of dampers are presented. The erratic behavior of damper in time domain and dominant frequencies are investigated.