Noise reduction

1) Introduction

The sound can be air or driving structural conduction. Most sources radiate sound both as otherwise. The following diagram shows that for noise reduction measures can be taken at various levels in the chain: at the source, about the means of propagation, interfaces and/or on the receiver.

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Evaluation of exposure of workers at vibrations – hand arm

1 -INTRODUCTION

During our day-by-day we are exposed to vibration, one way or another, in cars, buses, train, etc. Many people are also exposed to other vibrations, during your work, for example those produced by hand tools, machines or heavy vehicles.

Here will be only referred to the undesirable vibrations: the effect of overexposure to vibration; the various factors that should be taken into account when it is measured, How is measured and evaluated, and what actions can be developed to reduce sources of harmful and/or dangerous vibrations.

2 – NORMATIVE REFERENCES

Legal and regulatory references (in Portugal) are the following: Read more

Evaluation of exposure of workers at vibrations – whole body

1 -INTRODUCTION

During our day-by-day we are exposed to vibration, one way or another, in cars, buses, train, etc. Many people are also exposed to other vibrations, during your work, for example those produced by hand tools, machines or heavy vehicles.

Here are the undesirable vibrations: the effect of overexposure to vibration; the various factors that should be taken into account when it is measured, How is measured and evaluated.

2 – LEGAL AND REGULATORY REFERENCES

Legal and regulatory references (in Portugal) are the following: Read more

Evaluation of exposure of workers at vibrations – frequency weighting

FREQUENCY RESPONSE OF THE HUMAN BODY

To understand the reason why humans are more sensitive to some frequencies than others is useful to consider the human body as a mechanical system. The system is complicated by the fact that: (a) each body part has your greater sensitivity in different frequency ranges; (b) the human body is not symmetrical, e (c) There are no two people respond to vibrations in exactly the same way. Anyway, biomechanical models were developed suitable to simulate human response to vibration.

 

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Predicted noise levels within enclosures

The need to reduce the noise to acceptable values is an important priority for many companies. These noise reduction actions are often concerned significant investments, and we must ensure the success of the project and minimizing their costs, and this is a major concern of those responsible. Give the importance of objective approach exists as regards the assessment of the impacts of investments to make.
However, experience has shown that, often, and especially in the case of installations of large size and/or complexity, the measurements of noise levels, just for you, do not allow to get reliable results or a clear view of the real impact of the different sound sources. Read more

The discomfort generated by vibrations can also be evaluated

The discomfort generated by vibrations can also be evaluated

It is common to complaints of noise are associated with complaints of discomfort of vibrations. The fact that in Portugal there is a law of the noise and there is no law of vibration leads to complaints with respect to this last phenomenon is often ignored. However nowadays there are criteria for evaluating discomfort of vibrations in multiple countries and, therefore, nothing prevents do tests to evaluate the relevance of the complaints of the people. Read more

Noise bells

Sound of bells and sound amplification systems

Over the years the sound of bells coming assuming an increasingly significant expression in the universe of complaints for noise. Notwithstanding the Constitution, in your article 41, stating that the bells are a form of freedom of expression, through touch and with the passing of hours call to prayer, invoke festive moments or headstones, the noise produced by a public address system associated with the bells of a church must respect the limits set by the general regulation of noise, the drafting of Decree-Law No. 9/2007. Read more

workers' exposure assessment to vibrations - such as information transmitted to the test laboratory may influence the outcome

vibration information transmittedOne of the most important parameters for the calculation of the value of the exposure of workers at vibrations, is your length, This being provided by employers.
According to what is defined in the scope of accreditation of testing laboratories, If they are not transmitted the uncertainty associated with the duration of exposure times, This is defined as being of 4%. Read more

VIBRATIONS OF ASSESSMENT IN BUILDINGS – ANNOYANCE

DISCOMFORT OF VIBRATIONS

 

1 INTRODUCTION

When there are noise nuisance complaints very often occur simultaneously vibration nuisance complaints. Being the assessment of discomfort a difficult task, due to the subjective component of this human reaction, This difficulty increases because the, contrary to what occurs with noise, the criteria for discomfort of vibrations are not well established in Portugal. So who makes the assessment is often, in difficulty to draw conclusions. In this article pass in review the factors that influence the discomfort due to vibration, criteria used in evaluation and your requirements of measurement instrumentation.
2 HUMAN RESPONSE TO VIBRATION IN BUILDINGS
The following are the factors that influence human reaction to discomfort vibrations in buildings:
• Thresholds of perception
• Frequency response of the perception threshold of the human being
• vibration level
• Exposure time
• Type of vibration
• Type of use of the building
• Side-effects
• Time of day and activity of people
• The attitude of the people Read more

Noise reduction in the industry with noise maps – Part 2

Part 2

The approach of acoustic engineering

In order to reach the table presented above has been previously provided the following information, on estimated quantities and cost statements:

Map of noise reduction solutions

This map was based on the specification of necessary reductions:

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