Noise reduction in the industry with noise maps – Part 1


Nowadays society is strongly sensitive to environmental issues and sustainability. DECO estimates that in Portugal there are about of 800.000 people exposed to excessive noise and complaints concerning this, are the most common complaint with respect to the environment. The noise emission and the right not to occur to disturb are regulated and people are informed of their rights. So 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 for the environment. Give the importance of objective approach exists as regards the assessment of the impacts of investments to make.

Limitations of sound impact assessments "traditional"

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Evaluation Temporal Characteristics of Acoustic buzzer with a sound level meter

Drop Falling into WaterIntermittent noise, as well as the resulting impact, explosives or shots are more bothersome than stable and continuous noise – as the sound of rain – because I são sudden and unexpected. This type of noise can even trigger a reflex reaction scare, startle with effects not only psychological but also physical. However the only body back to its previous state after a few minutes.

Weighting Time

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A ISO 5349 defines the accelerometers must be rigidly mounted to effecting the measurements. The concept of rigidity derived from the definition function with one degree of freedom. Pursuant 5348 also recommends that the resonant frequency of the accelerometer shall be at least five times greater than the maximum frequency of interest which in the case of measuring the hand arm system is 1250 Prophet. Since the resonance frequency of the accelerometers typically used in these measurements much higher than this value, what is primarily concerned is the assembly of the resonance frequency.


In this article will be revised accelerometers mounting methods to perform these tests and the factors that must be taken into consideration in your selection.


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Noise measurement collective equipment of buildings

The common equipment noise measurement buildings, applies only if already are installed common equipmentin the building. (p. Ex.:. water pumps, exhaustion fans, elevators or other)

The laboratory performs verification by comparison with the legal requirements in Regulation of the acoustic requirements of buildings, approved by the D, L. 129/2002, republished the 9 June 2008 (integrating the changes described in D, L. 96/2008). Read more

Measurement of sound insulation

For measuring sound insulation are used the following indexes:
  • effective sound insulation
  • corrected sound insulation

The effective sound insulation D is defined simply as the difference in dB between the level in the emission room, L1, and the level at reception L2 : D = L1- L2.

This difference is given for each frequency band or globally . The ISO standard measurements use a noise (generally pink noise or noise of road traffic) in the emission room. The difference in levels may be given in octave bands or third octave bands, dB or dB(A).

Orders of magnitude of sound insulation:

– 35 dB(A) one can hear everything.
– 40 dB(A) the conversation is unintelligible.
-50 dB(A) the conversation is inaudible.

Corrected Sound Isolation Read more