1. An active resonant absorber for flexural waves in a rod
MARDiH 2009
Active Noise and Vibration Controls Methods
An active resonant absorber
for flexural waves in a rod
Nikolay KANEV, Alexey GLADILIN
N.N. Andreev Acoustics Institute
Moscow, Russia

2. Active resonator for sound control
MARDiH’07
Kanev N., Mironov M., Gladilin A., Dogadov A. A new approach to active noise control: active resonators // Proc. of 8th MARDiH, June 11-14, 2007, Krakow-Krasiczin, Poland. P
General conditions
for maximum scattering
and maximum absorption
of sound
Z – resonator impedance
Zr – radiation impedance
Ordinary resonator
Active resonator
max
max
Efficiency
Efficiency
Frequency
Frequency

3. Design of the active resonator
Active resonator is the device consisting of the loudspeaker, amplifier and microphone that operates to regulate the impedance of the loudspeaker in wide frequency band.
We regulate the loudspeaker impedance to satisfy the resonant condition.
Loudspeaker
Microphone P0 P1 U
Incident sound wave
Optimization of K
K()
Electrical feedback
U=(P0+P1)K()

4. Active resonator for flexural vibrations control
Vibrating surface
(rod, plate, shell, etc.)
Ordinary
resonator m
Flexural
wave κ
Impedance Z
Active
resonator
Feedback Fa Zf
Optimization
Sensor

5. Construction of active absorber
Magnet
Control
signal U2
Frequency
filter with amplifier
Core with the coil
Flexural wave
Hanger
Measured
signal U1
Vibrating
structure
Sensor
Impedance of the active resonator
- sensitivity of the sensor
- feedback coefficient

6. Active absorber for an elastic rod
Semi-infinite or bounded rod
Incident
flexural wave
Reflected
flexural wave
The incident flexural is absorbed fully when the resonator impedance is equal to

7. Experimental results Primary source Rod Vibrometer Active resonator

8. Experimental results Insulation of vibration, dB Frequency, Hz Source
Active resonator
Vibrometer
Absorbing structure
1.5 m
2.0 m
Insulation of vibration, dB
Frequency, Hz

9. Summary
The concept of the active resonator proposed recently for sound control is developed for flexural vibration control.
The mail idea consists in providing the resonant impedance of the secondary vibration source in wide frequency range.
It is proposed the construction of the active resonator, which consists of the electrodynamical actuator and the sensor measuring vibration velocity of the structure.
The active resonator is experimentally examined for absorption and insulation of flexural waves in the elastic rod.