Acoustic measurements in industrial soundproofing. An introduction to the main instruments and parameters

Noise mitigation endeavors frequently demand the assessment of diverse acoustic parameters in order to evaluate the efficiency of their noise reduction process.

The assessment of noise levels is essential indeed to establish adherence to noise-related regulations.

Noise evaluations might be necessary for diagnostic intentions or to pinpoint the origin (or origins) of sound within a machinery component.

Acoustic measurements can also be utilized to discern the routes taken by noise transmission within a system.

The article briefly introduces the main noise measurement instruments for industrial noise control environment.


Which acoustic measurement equipment is required?

Everything begins with the accurate selection of measurement instrument to monitor and measure sound properties.

When we have a basic scenario that needs assessing the severity of environmental noise, it might be sufficient to measure either the overall sound pressure level or the A-weighted level, employing a basic sound level meter. For instance, if the aim is to measure whether the sound level within a room surpasses 90 dBA, then utilizing a portable or hand-held sound level meter would be appropriate.

There are instances where a more comprehensive assessment of the noise is required instead.

In such situations, measurements involving octave band or 1/3 octave band sound levels may be conducted.

To conduct these measurements, a sound level meter furnished with octave band or 1/3 octave band filters is essential.

Alternatively, an acoustic spectrum analyzer that employs microprocessors to manipulate input data could be a recommended choice.

To ensure adherence to noise exposure regulations, dosi-meters can be employed to measure and record accumulated noise exposure.

Data on the sound power generated by machinery and equipment is crucial for creating more subdued mechanical systems, conducting acoustic evaluations among various machines, and identify key information concerning production machinery and equipment.


Noise measurement: main parameters

Measurement techniques play a crucial role in assessing noise properties and their impact on the environment, personnel health, and various applications. Several key parameters need to be fulfilled by these techniques to provide a holistic assessment of noise properties.

An article recently published by Occupational Health and Safety Blog identified six of them: (1) Sound Pressure Level (SPL); (2) frequency; (3) duration; (4) noise dose; (5) peak levels; (6) weighting.

Three of such parameters should be always measured in industrial noise control:

  • Constitutes the fundamental measure of sound magnitude, which is normally expressed in decibels (dB). In this case, the measurement instrument captures the fluctuations in air pressure induced by sound waves in relation to ambient atmospheric pressure.
  • Is about the frequency of sound wave cycles per second, which is normally quantified in hertz (Hz). Varied sounds exhibit diverse frequencies, prompting a comprehensive analysis of sound across its frequency spectrum.
  • Accounts for the temporal extent of sound. This aspect gains relevance while assessing prolonged noise exposure, particularly in occupational scenarios.


Sound level meter (SLM): one of the most widely used acoustic measurement instruments

Sound level meters are special equipment composed of a microphone, amplifiers, weighting networks, and a display indicating decibels.

The microphone acts to convert the input acoustic signal (acoustic pressure) into an electrical signal (usually voltage). This signal is magnified as it passes through the electronic pre-amplifier.

The amplified signal may then be modified by the weighting network to obtain the A-, B-, or C-weighted signal. This signal is digitized to drive the display meter, where the output is indicated in decibels. The display setting may be ‘‘fast’’ response, ‘‘slow’’ response, ‘‘impact’’ response, or ‘‘peak’’ response. Unless one is interested in measuring rapid noise fluctuations, the ‘‘slow’’ response setting is usually used.

An output jack may be provided to record or analyze the signal in an external instrument system. Sound level meters are rated in the following categories, based on the accuracy of the meter:

(a) type 1, precision;

(b) type 2, general-purpose;

(c) type 3, survey;

(d) special-purpose sound level meters.

There are several items of auxiliary equipment that are used with sound level meters, including a calibrator and a windscreen.

Many sound level meters have output ports for connection to a PC for post-processing of data.


Measurement services by Stopson Italiana

Stopson Italiana conducts measurements in accordance with main regulation on force. We can conduct various types of measurements, notably:

  • Acoustic measurements of the impact on neighbouring communities (temporal evolution in dBA, Leq measurement, 1/3 octave spectrum analysis) from 1.5m to 7m above ground level;
  • Acoustic impact measurements at property fence;
  • Residual noise acoustic measurements;
  • Exploratory acoustic measurements (acoustic research and characterization of sound sources, calculation of sound power levels emitted).

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