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

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. 225-232. 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

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()

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

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

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

Experimental results Primary source Rod Vibrometer Active resonator

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

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.