Noise Control Devices Research Articles

Method and apparatus for controlling noise

First Page

Application of a Noise Control Device with Interference Principle

Application of a Noise Control Device with Interference Principle

Research on a noise control device. (5th report The noise reduction effect of application to a machine and its prediction method by a scale model experiment)

The principle of the noise control device and its design methods were described in the previous reports, and it was indicated that a great noise reduction can be obtained when the noise control device with an appropriate barrier, that is, the noise control device system was used. Before the noise control device system is applied to a real noise source, for example, a machine noise, a traffic noise, etc., it is necessary to estimate the noise reduction effect. For this purpose, the noise reduction effect of application to a machine noise was measured and its prediction method by a scale model experiment was considered. In this paper, the noise reduction effect of application to a real noise source and its prediction method are described.

Research on a Noise Control Device : 3rd Report, The Fundamental Design of the Device (2)

Research on a Noise Control Device : 3rd Report, The Fundamental Design of the Device (2)

Research on a noise control device (4th report, The frequency dependence of the device and the contribution of each pipe to the noise reduction region.

The principle of the noise control device was described in the 1st report and the fundamental design method of the device was explained in the 2nd and 3rd reports. It is known from these studies that the acoustic design of the pipes composing the device is very important for studying the noise reduction region produced by the device ; and each pipe of the device has frequency selectivity. Therefore, it is necessary to study how the noise reduction region depends on a frequency, and how each pipe of the device contributes to the noise reduction region. These results are described in this paper.

How do we arrive at noise standards?

This paper describes the principal organizations responsible for the development of noise standards, discusses processes through which they are generated, and identifies the principal types of standards that exist. The majority of standards are developed voluntarily by the private sector, both in the USA and abroad. The American National Standards Institute (ANSI) coordinates American federated national standards system which in acoustics includes professional societies such as ASA, SAE, and ASTM and industry organizations such as NEMA, CAGI, and OPEI. ANSI also is the U.S. member of the organizations responsible for developing voluntary international standards. Participation in the development of ANSI and international standards in acoustics is open to all who have a direct and material interest. Voluntary standards cover all aspects of acoustics, including measurement, instrumentation, propagation, noise control devices, and human response criteria. In the USA, government standards or regulations are pr...

Research on a noise control device. 3rd report The fundamental design (2) of the device.

The structural design method of the noise control device was described in the 2nd report and it is possible to design the structure of the device by this method. But it is necessary to design how to set the device to the noise source when it is applied. That is, the appropriate set position to the noise source is required in order to obtain more noise reduction effect. Therefore, the design method for setting the device was considered through some model experiments in the anechoic room and the field, and the sound pressure level prediction method for the device with a barrier was obtained. These results are described in this paper.

Research on a Noise Control Device : 2nd Report, Fundamental Design of the Device (1)

This noise control device, which produces a greater noise reduction effect than a barrier is capable of refacting the sound waves and reducing a noise by destructive interference, and it consists of many pipes which make a structural delay circuit. It is very important to design the pipes of the noise control device such that the device may produce a great noise reduction effect when it is applied to noise pollution problems. This paper describes the fundamental design method of the pipes and refers to the experimental data in an anechoic room and some sound theories. As a result of this study, the fundamental design method of this noise control device has been established.

Research on a Noise Control Device : 1st Report, Fundamental Principle of the Device

This study is concerned with a newly developed facility for controlling noise propagation and thereby producing a wide region of reduced sound power, which is expected to be effective to alleviate railroad noise, highway noise, machine noise etc.. The mechanism of noise reduction by this device is destructive sound wave interference between refractive sound waves propagating through multiple passages of different lengths eqipped with the device and direct propagation sound waves. In this paper, the structure and principle of the facility are described and the technical data for practical application are collected.

The effect of a noise abatement program on reading ability

A school was selected for the testing of the effects of resilient rubber pads as noise control devices on a nearby elevated rail track. In addition three school classrooms received acoustical treatment to the ceilings. Teachers and students reported a quieter atmosphere after installation of the pads. Reading scores in the year prior to installation were lower on the noisy side of the building, but after installation of the rubber pads and the noise-absorbing ceilings there were no differences in reading achievement between children on the noisy side and those on the quiet side. Possible explanations of these findings and implications for social policy decisions are discussed.

Vibration damper for power saws

A noncontacting means for reducing vibration in, and noise radiation from a saw blade was first described at the San Diego Meeting of the Acoustical Society in November 1976. Some 15-dBAnoise reduction was demonstrated for a 10-inch radial-arm saw ripping a 1-in. thick maple board. The damper resembled a disk brake by its use of a caliper action to force damping elements toward opposite sides of the blade, but these elements are held out of contact by a thin film of pressurized air acting as a static air bearing, thus a negligible drag force acts on the moving saw blade. Improvements have been made and the application expanded to include metal and plastic cutting. The latest model is wholly contained within the saw guard so that it is substantially unnoticeable to the operator except that the operation is quieter. Arrangements are being considered for licensing agreements to manufacture and distribute commercial versions of this noise control device for various industrial sawing operations. Potentials and limitations for application of this damper to larger saw configurations will be discussed.

Analysis of highway noise

Highway noise will be discussed from the standpoint of planning and designing highways as well as the corresponding questions of land use in the adjacent corridor. In the location decision of a highway corridor and in choosing the specific highway alignment, the noise impact upon the adjacent community can be evaluated by predictive methods and compared to existing noise levels in that corridor. In such a way, one can compare the noise impacts of alternate location or alignment decisions in a manner consistent with applicable federal and state noise criteria. Once an alignment determination has been made the detailed design of the roadway including roadway elevation and the traffic operating characteristics can be addressed such that noise is minimized in the adjacent community. Factors by which highway noise may be further minimized by land use planning and proper design and construction of buildings near the highway itself will also be discussed. Sound propagation near an urban highway is an extremely complex matter because of the role which meteorological conditions play as well as the role of complex topography and the existence of man made structures. The technology for addressing the variety of these features by means of a computer model will be discussed, especially as this prediction method allows one to take into account future descriptions of highway traffic which can address traffic volumes, vehicle mix, vehicle speeds, future noise control devices at the vehicular source and other factors.

Calibration and Equalization of the Western Electric 640AA Microphone to 100 kc

Model testing of jet engine noise control devices has spurred high-frequency microphone development because of the importance of the high-frequency bands in the full-scale noise reduction. Calibration of the Western Electric 640AA microphone to 100 kc by free-field reciprocity has become routine in our laboratory. Some essential details of the technique and results of repeated calibration over a long period are reported. Use of reciprocal equalization in the complementary circuitry facilitates the use in noise analysis. Sensitivity and noise threshold of the 640AA microphone are excellent for model jet measurements.