Noise Abatement Techniques Research Articles

Adaptive noise abatement in automatic cab signaling receivers

Under conditions of a priori noise uncertainty, it is effective to use adaptive noise-abatement techniques to improve noise protection of continuous automatic cab signaling (CACS) receivers. The purpose of this article is to study the possibilities of an adaptive signal-processing technique, adaptive noise filtration (AF), providing better noise resistance of the CACS signals. To achieve this goal, the following problems are solved: a mathematical model of the CACS receivers' input signals is developed, a functional circuit and adaptation algorithm of a basic and a modified multichannel CACS receivers' adaptive filters is substantiated, and a computer simulation of adaptive filters is performed, confirming the accuracy of the obtained results and effectiveness of such filters for noise reduction. A distinctive feature of the proposed filters, which significantly expands their functionality, is a priori information on the presence of breaks in the CACS signals used in the adaptive algorithms.

Implementing Off-peak Deliveries in the Greater Toronto Area: Costs, Benefits, Challenges

Abstract Nestle Canada currently uses 32 routes that serve over 4,500 customers in the Greater Toronto Area (GTA). This study aims to quantify Nestlé's costs and benefits of modifying their ice cream supply chain to incorporate night-time deliveries, while providing a framework for the regulatory, conceptual, and inertial obstacles to implementation. Employing Nestlé's customer data set, we created routing software to determine the proportion of customers who must be willing to accept deliveries outside of normal working hours so that the change would be financially feasible. Based upon a literature review we found that, before proceeding, the following qualitative factors should be considered: safety, sustainability, regulatory concerns, truck noise, traffic, and congestion. Reduction of 3–10 percent in the number of routes may result from switching a suitable proportion of deliveries to night-time, achieving the minimum fleet size when 50–60 percent of locations are served on night routes. The operation of both night-time and daytime deliveries would enable an increase in truck utilization, thus decreasing the number of vehicles required. Recommendations for success of night-time deliveries include preparation of a safety plan, procurement of plate trucks, noise-abatement techniques, and the development of a noise-monitoring program.

Simulation of vibration and noise of belt gearing

The aim of this work is to find the methods of reducing noise and vibration in the belt drive of the electromechanical drive of the selected technological equipment. Thus, we are having more comfortable working conditions in the workplace in compliance with the sanitary standards of noise and vibration. The noise abatement techniques and the simulation of the vibration of the grinding woodworker flexible gearing are considered. Modeling was performed with the introduction of Euler variables. The simulated dependences allow by calculation determine noise levels and load characteristics of the selected equipment. The comparison between the expected noise levels and the sanitary standards allow determining the exceedance and the sources of its generation. All this is the basis for selecting the engineering solutions to observe the noise code.

A model for passive underwater noise suppression by bubble curtains surrounding point or line sources in shallow water

Underwater noise generated by pile driving, rotating machinery, or towers supporting offshore wind turbines may disturb marine life and inhibit detection of coastal activities via passive sonar and seismic sensors. Noise abatement techniques have therefore been proposed to limit the propagation of such noise into the far field, and many of these employ a curtain of freely-rising bubbles or tethered encapsulated bubbles to surround the towers [Lee et al., J. Acoust. Soc. Am. 131, 3507(A) (2012)]. An analytic model, based on a Green's function approach, is presented for the passive noise suppression provided by a discrete number of bubbles surrounding submerged point sources or pulsating cylindrical towers above horizontally-stratified layers of sediment. The sediment layers are modeled as viscoelastic media and the Green's function is derived via angular spectrum decomposition [Hay et al., J. Acoust. Soc. Am. 129, 2477(A), (2011)]. Simulations in which the bubbles are assumed to react independently to the incident field will be compared to those in which bubble-bubble interaction is taken into account. The effects of bubble size distributions and void fractions on noise suppression will be investigated for different source configurations. [This work was supported by the Department of Energy under Grant DE-EE0005380.]

An experimental study of sound generated by flows around cylinders of different cross-section

The sound radiated by rigid cylinders placed transversely in a uniform stream has been measured in an anechoic wind tunnel over a range of Mach numbers ( M = 0.09 – 0.2 ). The cylinders have different cross-sections, e.g., circular, square, rectangular, elliptic, and circular with lateral ribs or knurled surfaces. Different length to diameter ratios of the cylinders are also investigated. Results are presented as narrow band spectra, measured in the far field (acoustic as well as geometric). All spectra are presented with dimensionless (scaled) axes, as well as the original dimensional scales. It is shown that elliptic cross-sections are less noisy, compared to all other cylinders, but noise abatement techniques such as lateral ribs and knurled surfaces can also reduce tonal radiated noise. Two practical applications of these experiments are the reduction of radiated noise from pantographs of high-speed railway trains, and from the landing gear of modern passenger aircraft.

Noise Reduction Effect of Noise Barrier for Shinkansen Based on Y-shaped Structure

This article discusses noise abatement techniques for the Shinkansen high-speed railway. As a number of different types of sound barriers have been developed, this article presents scale-model experimentation and a recommendation for what it finds to be the most effective configuration, which is a y-shaped barrier with absorbing materials as well as acoustic tube arrays. This proposed barrier type was then field tested on running Shinkansen trains. The models, which consisted of eight different configurations, were created and placed in an anechoic chamber and were stimulated with a sound source and monitored with a microphone. The y-shaped model was accepted for its ability to dampen low-frequency noise in particular, as most of the configurations were relatively effective at high frequencies. Although the field test was less promising than the scale model, its tendencies were in agreement.

RAILWAY NOISE: THE PHYSICS OF AIRBORNE SOUND GENERATION AND PROPAGATION

Research efforts for railway rolling noise control have increase considerably over the past five years. In particular, the development of the TWINS program has made it possible to develop innovative solutions such as optimized wheels. New measurement techniques with microphone arrays allow for a more accurate and detailed description of the sources and thus lead to a better understanding of noise generation and radiation phenomena. Nevertheless, the origin and growth of roughness, especially on rails, requires further study. Noise abatement techniques are often trivial and do not differ much from earlier ideas. Therefore the effort should not only be directed to more research, but also towards implementation of the most promising solutions.

Noise Abatement Techniques in Southern Pine Sawmills and Planer Mills

Noise Abatement Techniques in Southern Pine Sawmills and Planer Mills

Noise abatmement techniques in southern pine sawmills and planer mills.

Noise abatement in sawmills and planer mills generally has been considered infeasible by the industry because of a combination of economic constraints and inadequate development of controls. Work by two mills in southern Georgia, utilizing their own materials and their in-house staff for installation, has successfully reduced their employee noise exposure. Noise was reduced in these mills from the high 90- and low 100-dBa levels to between the upper 80 s and lower 90 s. This was accomplished without excessive costs or major process and equipment changes. Abatement methods included properly positioned barriers, machinery isolation, double-wall enclosures, acoustically treated infee and outfeed tunnels, employee rotation, and machinery enclosures.

Helicopter noise certification

The object of noise certification is to reduce aircraft noise at source by incorporating internationally agreed limits into national civil airworthiness requirements. The operation of aircraft which fail to comply with these limits during type tests is prohibited, providing manufacturers with a powerful incentive to design quieter machines. In the case of helicopters, noise characteristics are ‘designed in’ at an early stage, making accurate noise predictions an essential prerequisite to the introduction of new civil helicopters. Noise certification will not only result in progressive reductions of helicopter noise, but will also change the character of the noise as the more intrusive sources are avoided, either by design or by the use of noise abatement techniques.

Noise abatement techniques and systems

First Page

A comparison of several theoretical noise abatement prediction methods for pipe lagging

With the increased emphasis on process and power plant noise control in recent years, various noise abatement techniques have been developed by theory and experiment. Among these has been the use of acoustical materials for wrapping or lagging noisy piping and equipment. Several prediction theories have been reported over the past few years to allow for the selection a priori of pipe lagging material dimensions and properties in order to reach predetermined noise reduction goals. A comparison of these prediction methods is undertaken using a variety of material dimensions and properties. These results are then compared with experimental data taken under controlled and consistent conditions. Practical advantages and deficiencies in the prediction methods are discussed.

Noise control of high-speed railways

Japanese National Railways is devoting efforts to environmental problems--particularly the noise and vibrations caused by Shinkansen trains. Target values have been set by the environmental agency for residential and commercial areas. Noise around elevated structures have been carefully measured. Noise abatement techniques have been utilized and are discussed. Techniques are being developed to minimize transmission of wheel-rail noise and that arising from vibration of structures.