Abstract
Active Noise Control (ANC) has been considered a promising technology for the abatement of acoustic noise from the mid-20th century. Feedback and Feedforward ANC algorithms, based on the destructive interference principle applied to acoustic waves, have been developed for different applications, depending on the spectrum of the noise source. Feedback ANC algorithms make use of a single control microphone to measure an error signal which is then employed by an adaptive filter to estimate the noise source and generate an opposite-phase control signal. The Fx-LMS (Filtered-X Least Mean Square) algorithm is mostly adopted to update the filter. Feedback ANC systems have proven to be effective for the abatement of low-frequency quasi-steady noises; however, different challenges must be overcome to realize an effective and durable system for high-temperature application. This paper aims at experimentally assessing the feasibility of a Feedback Fx-LMS ANC system with off-line Secondary Path estimation to be used in mid-size diesel gensets for the reduction of the exhaust noise. Several solutions are proposed, including the mechanical design, the development of the Fx-LMS algorithm in the LabVIEW FPGA programming language, and the key features required to prevent parts from thermal damage and fouling. The developed prototype was implemented on a 50-kW diesel genset and tested in a semi-anechoic chamber. The noise abatement inside the exhaust pipe and at different measurement points around the machine was evaluated and discussed, showing good potential for improving the acoustic comfort of genset users.
Highlights
The increasing demand for acoustic comfort and the more and more stringent legislation on noise pollution limits in the industrial field has moved the research toward innovative systems for noise abatement
This paper aims at experimentally assessing the feasibility of a Feedback Fx-LMS Active Noise Control (ANC) system with off-line Secondary Path estimation to be used in mid-size diesel gensets for the reduction of the exhaust noise
The ANC Fx-LMS algorithm was written in the LabVIEW FPGA language and compiled on a Xilinx Kintex-7 70T FPGA installed in a NI 9045 Compact RIO device
Summary
The increasing demand for acoustic comfort and the more and more stringent legislation on noise pollution limits in the industrial field has moved the research toward innovative systems for noise abatement. Passive silencers suffer for the big size which is required in order to abate low-frequency noise sources [1]. This issue is especially evident in industrial gensets, in which the most influent component of the overall noise (in terms of linear dB) is the combustion-related noise [2]; the effectiveness of traditional mufflers on the low-frequency spectrum moves in an opposite way than compactness requirements. ANC systems, based on the destructive interference principle, aims at attenuating an unwanted noise emitted by a general source before it reaches the area of interest. Several ANC solutions have been tested in many industrial and automotive applications, e.g., portable generators [4], automotive [5,6] and locomotive [7] mufflers, car [8], aircraft [9] and yacht [10] cabins, ventilation ducts [11], power transformers [12], sound-proof windows [13], up to the well-known active headsets
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