Stanislaw Wrona

Active reduction of device multi-tonal noise by controlling vibration of multiple walls of the device casing.

The aim of this paper is to verify the idea of active reduction of device and machinery noise by controlling the vibration of their casing. The Active Structural Acoustic Control (ASAC) technology known from the literature for reducing noise propagating through a single wall is going to be applied to multiple walls of the casing, thus globally protecting the user and environment from excessive noise generated by the machine or the device. Based on previous research by the authors, pairs of vibration actuators and sensors are installed on the walls in order to provide highest sound insulation efficiency. Two adaptive control strategies are investigated - feedfoward and Internal Model Control feedback, both with the adaptive Leaky Normalised Filtered-x Least Mean Square (FxLMS) algorithm used to update control filter parameters. The control systems are experimentally verified by using a laboratory set-up, in presence of a multi-tonal primary disturbance. Obtained results are reported, discussed, and conclusions for future research are drawn.

Identification of elastic boundary conditions of light-weight device casing walls using experimental data

Device and machinery noise can be reduced by controlling vibration of casing walls - such approach, referred to as the active casing approach, has been successfully applied by the authors in previous publications. It was observed that for an effective active control it is crucial to mount sensors and actuators at appropriate locations on the vibrating structure. However, an optimization process of sensors and actuators arrangement requires a precise mathematical model of such structure. In this research a cuboid light-weight casing is considered. A mathematical model describing walls of such casing requires parameters to be defined that cannot be delivered by the producer nor measured directly. The aim of this paper is to develop and evaluate an identification procedure of model parameters basing on experimental data - distinguished natural frequencies and modeshapes. A memetic algorithm is used to find optimal set of model parameters. Automatic classification of simulated modeshapes is employed. Obtained results are validated experimentally for multiple casing walls.

Defining the Optimal Number of Actuators for Active Device Noise Reduction Applications

It is possible to improve sound insulation of devices and machinery from the environment by appropriately controlling vibrations of their casings. When implementing this approach, there is a need to select efficient locations of actuators on each of the casing walls. A common solution is to employ an optimization algorithm to find favourable arrangement according to a given objective. One of the essential parameters of this process is a number of actuators to be optimized, but most often it is assumed a priori, without any proper considerations.

Impact of Boundary Conditions on Shaping Frequency Response of a Vibrating Plate - Modeling, Optimization, and Simulation

Abstract The aim of this paper is to further develop the original method proposed by the authors in their previous publications and submitted as a patent to shape frequency response of a vibrating plate according to precisely defined demands. The method is based on modeling the plate together with additional masses and ribs, and applying a sophisticated optimization algorithm, which issues arrangement of the masses and ribs. It has a very high practical potential. It can be used to improve acoustic radiation of the plate for required frequencies or enhance acoustic isolation of noise barriers and device casings. It can be utilized for both passive and active control. For the latter case it allows at the same time to optimally arrange actuators and sensors. In the paper there are presented, compared and discussed simulation results of the method for a plate with different boundary conditions: simply supported, fully-clamped and elastically restrained against rotation (corresponding to a mounting in a real device casing). Proposed optimization criteria are followed from practical scenarios, where precise modification of a vibrating plate frequency response is desired. The application of the proposed method for active control is also shown. The important additional outcome of the paper are guidelines on designing device casings in terms of rigidity in order to obtain their required vibration and noise isolation features.

Employment of Double-Panel Casing for Active Reduction of Device Noise

The idea of active casing is an approach to reduce device and machinery noise by controlling vibration of casing walls. The sound insulation efficiency of this technique for a single-plate casing was confirmed by the authors in previous publications. However, under specific circumstances, a dedicated double-panel structure can yield even higher noise reduction. The aim of this paper is to propose and evaluate by means of laboratory experiments the performance of a double-panel casing in comparison with a single-panel casing. An adaptive control strategy based on the Least Mean Square (LMS) algorithm is used to update control filter parameters. A low-frequency noise in the range up to 250 Hz is considered. Obtained results are reported, discussed, and conclusions for future research are drawn.