Optimization of the Location of Secondary Sources for the Active Engine Vibration Acoustic Noise Control in the Generator Room

2015 ◽  
Vol 766-767 ◽  
pp. 968-973
Author(s):  
T. Ramachandran ◽  
M.C. Lenin Babu
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Noise Control ◽  
Acoustic Noise ◽  
Active Noise Control ◽  
Pressure Level ◽  
Secondary Source ◽  
Secondary Sources ◽  
Quadratic Minimization ◽  
Room Model

The noise acoustic control in the interior of a diesel engine generator room model is studied and optimized. The finite element modelling and discretization of the engine room is carried out and the noise control is achieved using global active control of sound. The Genetic algorithm (GA) is used to find the optimized location of secondary sources to minimize the sound pressure level at receiver’s location. The secondary sources strengths for the active noise control system are computed using quadratic minimization acoustic potential energy. It is found that the sound pressure level at receiver’s location has been significantly reduced with changing the secondary source positions from arbitrarily to optimal location.

Active noise control system in a fire helmet – a proposal of the solution

2018 ◽  
Vol 558 (3) ◽  
pp. 11-15
Author(s):  
Leszek Morzyński ◽  
Grzegorz Szczepański
Keyword(s):  
Control System ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Noise Control ◽  
Active Noise Control ◽  
Warning Signal ◽  
Verbal Communication ◽  
Pressure Level ◽  
Emergency Vehicle ◽  
Active Noise

An auditory warning signal emitted by a moving emergency vehicle is intended to inform other road users about an approaching emergency vehicle and the need to give way to it. Emission of a warning signal with the highest possible sound pressure level is the main method of ensuring the audibility and recognition of the warning signal by traffic participants at unknown and varying traffic noise, acoustic insulation of vehicles and noise in the interior of the vehicle. The A-weighted sound pressure level of the auditory warning signal reaching the interior of an emergency vehicle may exceed 90 dB, which can be harmful to the hearing, can adversely affect psychophysical fitness of the crew members and can significantly hinder verbal communication in the vehicle. This article presents the concept and results of numerical simulations of an active noise control system in fire helmets, which will reduce the exposure of the crew to the warning signal and improve the quality of verbal communication in an emergency vehicle. This system is integrated with the signal generation system. The Notch algorithm and the NLMS adaptation algorithm were used in the system's control algorithm. The construction of the controller was based on a microcontroller from the STM32F4 family.

scholarly journals First investigation on the applicability of an active noise control system on a tracked tractor without cab

2013 ◽  
Vol 44 (2s) ◽  
Author(s):  
Daniele Pochi ◽  
Roberto Fanigliulo ◽  
Lindoro Del Duca ◽  
Pietro Nataletti ◽  
Gennaro Vassalini ◽  
...  
Keyword(s):  
Sound Pressure Level ◽  
Digital Signal Processor ◽  
Sound Pressure ◽  
Engine Speed ◽  
Noise Control ◽  
Active Noise Control ◽  
Control Unit ◽  
Pressure Level ◽  
Maximum Speed ◽  
Active Noise

In last years, several research teams pointed their attention on the application of active noise control systems (ANC) inside the cabs of agricultural tractor, with the purpose of reducing the driver exposition to noise, that is only partially controlled by the frame of the cab. This paper reports the results of a first experience that aimed at verifying the applicability of an ANC on a medium-high power, tracked tractor without cab. The tested tractor was a Fiat Allis 150 A, equipped with rear power take off, used in the execution of deep primary tillage in compact soils. It is a tracked tractor without cab, with maximum power of 108.8 kW at 1840 min–1 of the engine. The ANC consists of a control unit box based on a digital signal processor (DPS), two microphones, two speakers and a power amplifier. The instrumentation used in noise data collecting and processing consisted of a multichannel signal analyzer (Sinus - Soundbook), a ½” microphone capsule and an acoustic calibrator, both Bruel & Kjaer. The study aimed at evaluating the behaviour of the ANC by means of tests carried out under repeatable conditions, characterized by pre-defined engine speed values. Three replications have been made for each engine speed. The sampling time was 30 s. Two series of tests were performed in order to compare the results observed with the ANC on and off. The engine speed adopted in the study ranged from 600 min– 1, up to 2000 min–1 (maximum speed) with steps of 100 min–1. The ANC proved to be effective in the interval of speed between 1400 and 1700 min–1, where the samplings have been intensified, adopting steps of 50 min–1. In such an interval, the attenuation observed with the ANC system on appeared evident both as weighed A sound pressure level (from 1.29 up to 2.46 dB(A)) and linear (from 4.54 up to 8.53 dB). The best performance has been observed at the engine speed of 1550 min–1, with attenuations, respectively of 2.46 dB(A) and 7.67 dB. Outside of the engine speed interval 1400 - 1700 min–1, the attenuations always resulted lower than 1 dB(A) for the weighed A sound pressure level and between 0.66 and 7.72 dB.

Variation in vibro-acoustic noise due to the defects in an automotive drum brake

2021 ◽  
Vol 263 (4) ◽  
pp. 2646-2653
Author(s):  
Ananthapadmanabhan Ramesh ◽  
Sundar Sriram
Keyword(s):  
Analytical Model ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Transfer Functions ◽  
Acoustic Noise ◽  
Pressure Level ◽  
Acoustic Model ◽  
Drum Brake ◽  
Non Linear ◽  
Sound Pressure Levels

Drum brakes are significant contributors to noise and vibration in automobiles causing discomfort to the passengers. The vibration and hence the resulting noise increase due to various inherent defects in the drum brake, such as asymmetry. This work aims to quantify the variation in the vibro-acoustic noise due to several common defects in the drum brake using an integrated non-linear vibration analytical model and a numerical acoustic model. The sources of vibro-acoustic noise sources such as contact and reaction forces are predicted using a four-degree-of-freedom non-linear contact mechanics based analytical model. A finite element based acoustic model of the drum brake is utilized to predict the force to the sound pressure transfer function in the drum brake. Product of the transfer functions and the forces gives the corresponding sound pressure level from which the overall sound pressure levels are estimated. The variation in the overall sound pressure levels due to different drum brake defects is evaluated by introducing defects to the analytical model. The results show that the overall sound pressure level is a strong function of the defects. It is envisioned that the current work will help in the development of effective health monitoring systems.

scholarly journals Identification and analysis of noise sources in the Noor-Abad gas compressor station, Iran

2015 ◽  
Vol 4 (1) ◽  
pp. 196
Author(s):  
Nader Mohammadi ◽  
Kami Mohammadi
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Acoustic Noise ◽  
Noise Pollution ◽  
Residential Area ◽  
Pressure Level ◽  
Compressor Station ◽  
Noise Condition ◽  
Noise Sources ◽  
Noise Map

The objective of this study is to identify the sources of acoustic noise (noise pollution) in the Noor-Abad gas compressor station and then to prioritize the station equipment based on noise pollution. First, the key locations inside the station as well as in the surrounding residential area, aka the study area, are determined for the measurement of sound pressure level. Then, the sound pressure level is measured at those points, and the related noise map is produced. Based on the noise map, the noise condition in the study area is evaluated by comparing the measured acoustic parameters with allowable standard values. Dangerous regions and critical points are thus identified. The major noise sources consist of main blowdown, units’ blowdowns, scrubbers, and turbo-compressors. The sound pressure level of main blowdown is measured at two intervals from its position: 80 m inside the station and 600 m outside the station (at the edge of the surrounding residential area). Also, the sound pressure level for a unit blowdown and a scrubber is measured at respectively 25 m and 40 m from their positions. Finally, the station equipment is prioritized based on noise pollution. The analysis of measurement results showed that the main noise sources are, respectively, the station main blowdown, units’ scrubbers, units’ blowdowns, turbo-compressors, and gas pipelines.

A Study on the Far-Filed Sound Pressure Level of Rectangular Plate Based on Fourier Transform

2013 ◽  
Vol 753-755 ◽  
pp. 1779-1784
Author(s):  
Ren Wen Dai ◽  
De Shi Wang ◽  
Yong Yong Zhu
Keyword(s):  
Fourier Transform ◽  
Rectangular Plate ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Active Noise Control ◽  
Pressure Level ◽  
External Excitation ◽  
Approximation Solution ◽  
Transform Method ◽  
Line Force

The far-filed approximation solution was derived in a closed formula by using Fourier transform method. Two kind of possible concentrated forces, a line force, a point force, were included in the analysis. Moreover, a parametric study was carried out to clarify the effect of the incentive loading position and the various physical characteristics parameters of the rectangular plate. Conclusion is drawn that, the far-filed pressure level decreased with external excitation approached to the edge. Through analysis on far-filed sound pressure level, that can give foundation of designing acoustical elements and active noise control.

Active Noise Control to Reduce the Blade Tone Noise of Centrifugal Fans

1988 ◽  
Vol 110 (3) ◽  
pp. 377-383 ◽  
Author(s):  
G. H. Koopmann ◽  
W. Neise ◽  
W. Chen
Keyword(s):  
Sound Pressure ◽  
Noise Control ◽  
Control Method ◽  
Reference Signal ◽  
Active Noise Control ◽  
Perforated Plate ◽  
Aerodynamic Noise ◽  
Secondary Sources ◽  
Active Noise ◽  
Centrifugal Fans

This paper describes an active noise control method to suppress the blade tones of centrifugal fans. Two secondary sound sources are mounted into the cutoff region of the fan casing. These sources are driven with electrical signals that are synchronized with the rotation of the impeller, and their amplitudes and phase are adjusted to give maximum reduction for the blade tone levels in the inlet and outlet duct of the fan. With this design, the sound emitted by the secondary sources is introduced into the interior of the casing near the source region where the blade tone is generated, i.e., the cutoff. The present experiments were concentrated on the reduction of the fundamental of the blade tone for centrifugal fan with impeller diameters between 280 mm (11 in.) and 710 mm (28 in.). Two different designs of secondary sources were investigated. In the first, two loudspeakers are contained within an enclosure which has an open end made of a curved perforated plate which replaces part of the original cutoff. The second design incorporates two vibrating plates which replace portions of the outlet duct side and the volute side of the cutoff. Reductions in tone sound pressure level of up to 23 dB have been observed for a variety of aerodynamic loading conditions and fan inlet geometries. To obtain a better understanding of the physical mechanism of this active noise control method, sound pressure measurements were also made on the inner surface of the fan casing along the volute. Both amplitude and phase of the blade passing frequency component were measured relative to a reference signal derived from the impeller rotation. The result of this experiment is that the sound field inside the casing is dominated by the pressure pattern rotating together with the impeller. Since the impeller tip Mach number is well below sonic speed, however, the radiation efficiency of the rotating pressures is very low. The blade tone noise measured in the far-field is generated by the unsteady pressures at the cutoff which in turn are produced by the flow leaving the impeller. This aerodynamic noise generating mechanism is modified by the active sources located in the cutoff.

Jackhammer Chisel Noise Control

2015 ◽  
Author(s):  
Henry A. Scarton ◽  
Kyle R. Wilt
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Noise Control ◽  
Pressure Level ◽  
Longitudinal Impact ◽  
Geometric Properties ◽  
Longitudinal Modes ◽  
Transverse Bending ◽  
Severe Reduction

A robust chisel damper for quieting a jackhammer is presented. The noise produced from a jackhammer chisel is dominated by the ringing of the chisel moil resulting from impacts of the internal hammer against the end of the chisel producing airborne radiation of the transverse bending and longitudinal modes. A model steel chisel moil point was constructed with geometric properties similar to a jackhammer chisel and designed so as to not fail during severe acceleration impacts from the reciprocating hammer. Anechoic tests of the maximum overall unweighted sound pressure level for the undamped chisel due to a longitudinal impact was 86.8 dB linear (re. to 20 μ Pa) at 1 meter with the strongest ring tone at 1.37 kHz and harmonics; the overall sound pressure level for the damped chisel with identical axial impacts was reduced by 16.5 dB to 70.3 dB with severe reduction of 40 dB of the dominant chisel ring tone, and the harmonics.

Application of a Multipole Secondary Source for Propeller Active Noise Control

2014 ◽  
Vol 564 ◽  
pp. 135-142 ◽  
Author(s):  
Muhammad Kusni ◽  
Benjamin Soenarko ◽  
Harijono Djojodihardjo
Keyword(s):  
Noise Reduction ◽  
Noise Control ◽  
Free Field ◽  
Active Noise Control ◽  
Secondary Source ◽  
Frequency Noise ◽  
Secondary Sources ◽  
Active Noise ◽  
Novel Approach ◽  
Active Noise Reduction

The commercial feasibility of active noise control (ANC) is very promising due to its capability beyond passive noise control (PNC). To some extent ANC becomes a complement of PNC. The active noise reduction is also capable and beneficial in reducing noise selectively. However, the active noise reduction using a conventional secondary source can become very complicated if a significant noise level reduction is required, since a large number of secondary sources will be needed. The active noise reduction is also less effective for reducing high-frequency noise. With such perspectives, a novel approach has been developed using a multipole secondary source to addressthe problems mentioned. In addition, the multipole secondary source will be used for numerical simulation of noise reduction in of propeller noise source in a free field.

Simulation and Analysis of Noise Control Scheme for Hangzhou Cigarette Factory New Packing Workshop

2014 ◽  
Vol 675-677 ◽  
pp. 217-224
Author(s):  
Yan Ping Wang ◽  
Xin Zhong Li ◽  
Yue Chao Wu ◽  
Jun Hao
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Noise Control ◽  
Pressure Level ◽  
Working Environment ◽  
Analysis Method ◽  
Control Scheme ◽  
Packaging Machine ◽  
Noise Test ◽  
Machine Station

Based on the noise test data of existing workshop, the noise of new packing workshop was studied. The effection of several noise control scheme was predicted by simulation and analysis method, and the control scheme five was chose finally ,by which average noise reduction was about 4.5dB,and 8h equivalent continuous A-weighted sound pressure level of the pick-up coil station and packaging machine station was 84.9dB and 83.2dB respectively, the working environment of the new workshop was effectively improved, and the investment was estimated.

Contributions of Voice and Nonverbal Communication to Perceived Masculinity–Femininity for Cisgender and Transgender Communicators

2020 ◽  
Vol 63 (4) ◽  
pp. 931-947
Author(s):  
Teresa L. D. Hardy ◽  
Carol A. Boliek ◽  
Daniel Aalto ◽  
Justin Lewicke ◽  
Kristopher Wells ◽  
...  
Keyword(s):  
Fundamental Frequency ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Vocal Tract ◽  
Presentation Mode ◽  
Pressure Level ◽  
Presentation Modes ◽  
Audiovisual Stimuli ◽  
Vocal Tract Resonance ◽  
Point Light

Purpose The purpose of this study was twofold: (a) to identify a set of communication-based predictors (including both acoustic and gestural variables) of masculinity–femininity ratings and (b) to explore differences in ratings between audio and audiovisual presentation modes for transgender and cisgender communicators. Method The voices and gestures of a group of cisgender men and women ( n = 10 of each) and transgender women ( n = 20) communicators were recorded while they recounted the story of a cartoon using acoustic and motion capture recording systems. A total of 17 acoustic and gestural variables were measured from these recordings. A group of observers ( n = 20) rated each communicator's masculinity–femininity based on 30- to 45-s samples of the cartoon description presented in three modes: audio, visual, and audio visual. Visual and audiovisual stimuli contained point light displays standardized for size. Ratings were made using a direct magnitude estimation scale without modulus. Communication-based predictors of masculinity–femininity ratings were identified using multiple regression, and analysis of variance was used to determine the effect of presentation mode on perceptual ratings. Results Fundamental frequency, average vowel formant, and sound pressure level were identified as significant predictors of masculinity–femininity ratings for these communicators. Communicators were rated significantly more feminine in the audio than the audiovisual mode and unreliably in the visual-only mode. Conclusions Both study purposes were met. Results support continued emphasis on fundamental frequency and vocal tract resonance in voice and communication modification training with transgender individuals and provide evidence for the potential benefit of modifying sound pressure level, especially when a masculine presentation is desired.

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