Fine-tuning acoustic isolation in buildings

MADRID - Dec. 2, 2013 - PRLog -- As research and design is vital to keep the company at the cutting edge in relation to technological developments, ACCIONA Infrastructure created a team to analyse noise and vibration. Where traditional acoustic isolation calculation methods show important deviations, ACCIONA Infrastructure’s research is improving results by refining the methodology and - ultimately - improving building designs.

In 2007, following the publication of the Spanish Technical Building Code (CTE), ACCIONA decided to carry out acoustic quality analysis on buildings. They wanted to develop their understanding of the sound isolation required and thus improve future designs. For this they created the Acoustics Group.

To perform the assessments, ACCIONA Infrastructure acquired two types of tools - calculation and simulation (for acoustic assessment on building projects) and measurement (for on-site analysis).

In practise, the Acoustics Group collaborates with the relevant construction project manager to ensure they cover all the details of the work process at the different construction stages; the project phase, early and advanced stages - and also after work has been completed. In this way, an exhaustive study of the acoustic behaviour of buildings can be performed throughout the process, from beginning to end.

Traditional acoustic isolation calculation methods show important deviations for various reasons - for example, the approaches taken to the characteristic parameters of building structures and the influence of the joint compression on the vibration reduction index (Kij), etc. These deviations usually cause an overdesign of the building structures, which ACCIONA Infrastructure is striving to avoid.

“The experience gained in successive years forced us into a more advanced approach,” says Raquel Cortinat, an engineer with ACCIONA Infrastructure’s Acoustics Group. “To reduce these deviations, as well as those arising from incorrect installation, our line of research starts by focusing on the calculation and measurement of building sound isolation.”

“The first step was to model new types of joints through Statistical Energy Analysis (SEA). We tried to obtain simple expressions that represent the Kij for new structural joints, which are not included in the current standards. At the same time, we have started to perform on-site measurement of Kij according to ISO 10848-1: 2006, in order to get information about the different types of joint behaviour.”

As in modal analysis, this actual test information is used to check and refine modal models.

For on-site buildings analysis, ACCIONA decided to start with a complete set of equipment to measure acoustic parameters. This included Brüel & Kjær’s Hand-held Analyser Type 2250, Omnipower Sound Source Type 4292 and Tapping Machine Type 3207.

ACCIONA Infrastructure contacted Brüel & Kjær again when they needed to undergo a more complex line of research - with more channels and parameters - before deciding on a PULSE data acquisition and analysis system.

Gloria Valverde, an engineer with the Acoustics Group explains: “PULSE software and LAN-XI Data Acquisition Hardware are the most appropriate tools for us to carry out this measurement in a simple way. The recording audio option was very useful for us. In many on-site cases where the measurement conditions are not controllable, signals that are not perceived may be affecting the measurement. Recording all signals can help us discard what does not interest us. One of the advantages of PULSE is that data can be easily exported to ASCII format and processed by other mathematical calculation software such as PULSE Reflex.”

The full ACCIONA case study is available to read on Brüel & Kjær's website.

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About Brüel & Kjær
Brüel & Kjær is a world-leading manufacturer and supplier of sound and vibration measurement systems. Brüel & Kjær helps its customers measure and manage the quality of sound and vibration in their products and in the environment. Focus areas are aerospace, space, defence, automotive, ground transportation, airport environment, urban environment, telecom, and audio.