A Compensated Acoustic Actuator for Systems with Strong Dynamic Pressure Coupling

Abstract

Audio speakers are commonly used as acoustic actuators for noise control applications. Recent developments in the use of compensated dual-coil speakers have improved the performance of these acoustic actuators. However, the performance of these speakers depends on the application. When they are applied in systems with strong coupling between the plant and the actuator, the velocity sensor used in previous work must be improved.This study considers the application of a compensated speaker as an actuator. An acoustic duct is used an as example of a plant that exhibits strong dynamic pressure interaction with the actuator. The speaker dynamics and the acoustic duct dynamics are first modeled separately. The two systems are then coupled, and the resulting system is modeled. A velocity sensor is developed and used in feed-back compensation. The resulting speaker system behaves as an ideal actuator with minimal magnitude and phase variation over a 0 -200 Hz bandwidth. These conclusions are verified through experimental results.This study is important in the overall area of acoustic actuators and active noise control. The actuator developed here will significantly aid in the goal of active noise control in an acoustic duct.

Actuator placement and zero effect on global wide‐band noise reduction in ducts with hybrid system identification technique

“…However, there is limited performance seen in real experiments , primarily because of an actuating subsystem associated with the real experiments. In an attempt to incorporate actuating dynamics into ANC design, efforts have been made to describe a theoretical model of an acoustic duct with a specific actuator such as an end-mounted speaker (Venugopal and Bernstein, 1998) or a side-mounted speaker of dual voice coils (Birdsong and Radcliffe, 1999). In real applications, there are different types of actuators for ANC control and various structures for mounting speakers such as side-tubes.…”

Combined Feedback Design of Active Noise Control and Face Velocity Control Based on a Novel Secondary-Path Model of Speaker-Duct Systems

“…The speaker-face velocities are affected by input voltages of e r (t) and e 1 (t) of the noise and DVC speakers as well as pressure loadings of p n (t) and p a (t) on the speaker faces (7), (8) . Thus, they can be depicted aŝ…”

“…However, an effect of sound pressure on the actuator speaker face velocity is ignored in the current ANC systems for most of the cases; the occurrence of a strong sound pressure on the actuator speaker face velocity may significantly obliterate ANC performance. In an attempt to reduce the effect of sound pressure on face velocity of actuator speaker, various face velocity sensors (5) - (8) are proposed and motional feedback (9), (10) technique is developed to control actuator speakers. Nonetheless, this feedback technique may increase response for higher order modes of face velocity of actuator speaker, hence causing a potential instability problem in ANC applications.…”

An Electronically Tunable Resonator for Noise Control

“…/" Figure 1: Ideal Helmholtz Resonator (Birdsong, 1999) The mass of air in the neck will oscillate in response to the wave as a solid body with effective inertia (2) where Ie and S are the effective length and cross sectional area of the neck. When dissipation is small, resonance occurs at a frequency…”

“…A speaker velocity estimator (Birdsong and Radcliffe, 1999;Radcliffe and Gogate, 1996) was implemented by combining the voltage in the secondary coil with the current in the primary coil. After the speaker compensator was implemented.…”