Active control of multi-dimensional random sound in ducts
Previous work has demonstrated how active control may be applied to the control of random noise in ducts. These implementations, however, have been restricted to frequencies where only plane waves are propagating in the duct. In spite of this, the need for this technology at low frequencies has progressed to the point where commercial products that apply these concepts are currently available. Extending the frequency range of this technology requires the extension of current single channel controllers to multi-variate control systems as well as addressing the problems inherent in controlling higher order modes. The application of active control in the multi-dimensional propagation of random noise in waveguides is examined. An adaptive system is implemented using measured system frequency response functions. Experimental results are presented illustrating attained suppressions of 15 to 30 dB for random noise propagating in multiple modes.
The implication of using remote sensors in active control of higher order acoustic duct modes
Abstract The active control of broadband noise in duct systems has achieved enormous success in the past two decades. To alleviate the Active noise control (ANC) system for higher order duct modes requires the development of a multi-modal control system. Previously, the performance of such an ANC system has been evaluated at the error microphone position. In this paper it will be shown that the performance of such a multi-modal ANC system can be misleading if it is not measured at a set of remote (monitoring) sensor locations which are further downstream than the error sensors used by the adaptive controller. Experimentally, the performance between two control strategies, namely Independent Modal Control (IMC) and Fully Coupled Control (FCC), have been compared at both error and monitoring microphones of a circular duct setup.
Proposed beam diagnostics instrumentation for the LANSCE refurbishment project
Presently, the Los Alamos National Laboratory is in the process of planning a refurbishment of various subsystems within its Los Alamos Neutron Science Center accelerator facility. A part of this LANSCE facility refurbishment will include some replacement of and improvement to existing older beam-diagnostics instrumentation. While plans are still being discussed, some instrumentation that is under improvement or replacement consideration are beam phase and position measurements within the 805-MHz side-coupled cavity linac, slow wire profile measurements, typically known as wire scanners, and possibly additional installation of fast ionization-chamber loss monitors. This paper will briefly describe the requirements for these beam measurements, what we have done thus far to answer these requirements, and some of the technical issues related to the implementation of the instrumentation.