LINES OF RESEARCH

NHOA project funded by ACC10 (FEDER 2015-2017). (See more)

Acoustic software to calculate the acoustic insulation of multiple and constructively complex walls (presence of stiffeners, etc.) is indispensable for any acoustic. However, most existing software uses excessive and unhelpful simplifications to make accurate noise forecasts. ICR, as a soundproofing company has developed acoustic insulation calculation software to try to mitigate this problem. This has been based on a combination of theoretical methods and laboratory measurements to adjust forecasts as much as possible to reality. The result has been a software that not only takes into account complex multi-walled systems, but also considers the coupling between low-frequency premises and indirect noise transmission paths. Its main applications include room soundproofing, acoustic conditioning and the calculation of sound insulation and soundproofing.

ICR has participated in the definition and characterization of recycled materials to be used in the construction of acoustic barriers. The use of recycled materials has allowed a considerable reduction in production costs while contributing to recycling and environmental preservation.

The needs of industrial acoustic in sectors such as gas or oil require increasingly more and more techniques to monitor the state of the installations, which represent an intrusion in the production process. Noise and vibration analysis techniques to detect the presence of blockages inside ducts are an alternative for the future. These techniques capture the dynamic behaviour of the inner acoustics of the pipe and make it possible to determine the percentage of blocked pipe cross-section due to impurities deposition. ICR, together with the Italian oil company ENI, is carrying out a research project to develop systems to obtain information on the sealing of conducts from vibration control on their surfaces.

A correct understanding of the phenomenon of plate vibration, as well as its computational and analytical simulation are fundamental for anyone facing a problem of vibroacoustic origin. The use of computational methods is of great help and are often the only possible alternative in the case of geometrically complex structures. However, it is very convenient to have analytical methods as they allow a quick evaluation of the dependency of the vibration levels of the structure according to its basic parameters. In practice many structures can be approximated (at least in a first phase) as simple plate and beam combinations, and analytical methods are useful.
At ICR, research has been carried out in both directions, both from the computational point of view, developing finite element methods that use class C0 form functions to address problems of thin plate bending, and from the analytical point of view, developing methods that consider plate sets with different types of joints and contour conditions. Recently, progress has been made in applying the GTDT method to plate problems, since it allows simulating the effects of blocking different degrees of freedom at certain points of these.

ICR is developing a methodology to predict the influence of aerodynamic excitation on the internal noise of high-speed trains. The methodology consists of several phases: the first is to perform very diffusive CFD simulations of airflow around the train, in order to capture pressure fluctuations on its surface. In a second phase, these pressures are introduced into a finite-element mechanical model that characterises the roof of the train (or other surfaces of interest such as the windscreen or windows) and from its vibration the acoustic power is obtained.
Finally, this acoustic power is introduced in an acoustic computational model of the train that contains the rest of the noise sources of the train (roller, auxiliary equipment, engines, etc.) so that we can determine the importance of aerodynamic excitation in the front of the other sources. As regards excitation due to the blocking pressure of the turbulent boundary layer, standard models are used and a similar procedure is followed.

In recent decades, successes in the fight against vibroacoustic noise in vehicles have been remarkable. As a consequence, the noise of aeroacoustic origin (i. e., noise generated by non-stationary and/or turbulent air flows and their interaction with solid surfaces) has occurred increasingly important and in many cases the new adversary to overcome. If we combine this with the fact that land vehicles are travelling at ever-increasing speeds (high-speed trains) the need for analysis and forecasting tools in aeroacoustics becomes very clear. In this sense,ICR has made a strong commitment to computational aeroacoustics (CAA).
ICR has contributed significantly to the development of finite element codes for computational fluid dynamics (CFD) and computational aeroacoustics. The use of so-called acoustic analogies in order to calculate the aerodynamic noise generated by subsonic fluxes, requires CFD simulation to obtain the terms that act as an acoustic source, and a subsequent resolution of the inhomogeneous wave equation to obtain the desired acoustic field. CFD simulation presents numerous difficulties, especially for turbulent fluids, and the relationship of turbulent LAS (Large Eddy Simulation) models with the mathematical stabilization methods used in the numerical resolution of Navier-Stokes equations is currently being investigated. Acoustic simulation also presents difficulties, especially with regard to the occurrence of the so-called pollution error in the numerical resolution of the Helmholtz equation.

The theory of the inverse problem is based on a Bayesian interpretation of probability calculation. It was largely developed by geophysicists in their quest to model the interior of the Earth from data collected on the surface. Its application to various industrial cases has allowed us to successfully solve two problems, one of a scientific nature and the other of a practical nature. The first refers to the objective always sought after in acoustics, to know the contribution of different noise sources to the total level measured at a given point or location, from which the noise is to be reduced. For example, the reversal of models allows us to obtain the acoustic power of different noise sources in a factory from measurements of the acoustic field they generate. The second problem is precisely that of being able to carry out these measures without interfering with the operation of the factory and within a reasonable period of time. The inversion of models makes these issues feasible as it is a non-intrusive and quick application technique.
In the case of the automobile, and in a research project contracted by Ferrari Auto,ICR was able to develop a methodology based on the theory of the inverse problem, to determine the noise inside the cabin in the mid and high frequency range. The method reduced the process of obtaining the acoustic power of the cabin surfaces from 30 to 2-3 days.
The theory includes the use of various optimization techniques and careful analysis of stability and validity of solutions through techniques such as resampling.

ICR has developed the GTDT method (Global Transfers and Direct Transfers) of transmission path analysis. The method establishes the connectivity relationships between the different subsystems of a network that represents a certain physical model to analyze. This allows, for example, to know the contributions of the vibration of the different surfaces (subsystems) into which the passenger compartment of a vehicle can be divided, to the total acoustic noise received by the occupants.
The key to the method lies in the fact that the calculated contribution of each surface is independent of the vibration of the other surfaces of the passenger compartment. In other words, the method allows us to move from a coupled physical system in which the vibration of each subsystem is affected by the influence of the rest of the network subsystems, to a decoupled system in which the contribution of each subsystem to total noise is obtained, with the rest of subsystems mathematically blocked.
In this way, it is possible to predict the individual contribution of each surface area to total noise and the order in which it is to be treated in order to achieve the desired noise level. The same treatment can be carried out if the vibration level of a particular subsystem is to be reduced.
Currently, research within the scope of the GTDT method has both theoretical and experimental aspects aimed at optimizing measurement methods, improving equation solving systems through regularization and resampling treatments, addressing the case of non-linear networks and applying the method to a wide variety of cases.

LIST OF PUBLIC FUNDING RESEARCH PROJECTS

1-“ECO-PLAK: Fase 1”
CIDEM Project of the Generalitat de Catalunya
Duration: 1996 to 1997

2-“Portable Sound Imaging”
ESPRIT project of the European Community
Ref: ESPRIT 21 040
Duration: 1995-1998

3-“STBM: Tunnel Boring Machines”
European Community BRITE project
Ref: BRITE BE95-1735
Duration: 1995-1998

4-“ECO-PLAK: Fase 2”
CIDEM Project of the Generalitat de Catalunya
Duration: 1999-2000

5-"PAASC: Sound Insulation Software in Complex Systems"
CIDEM Project of the Generalitat de Catalunya
Duration: 2000-2001

6-Noise reduction in railway products through advanced experimental methods. Phase 1 "
PROFIT Project of the Ministry of Science and Technology
Ref: FIT-020300-2002-24
Duration: 2001-2002

7-Noise reduction in railway products through advanced experimental methods. Phase 2 "
PROFIT Project of the Ministry of Science and Technology
Ref: FIT-020300-2002-24
Duration: 2002-2003

8- "MACIM: Computational Aeroacoustics Models for the Reduction of Environmental Impact of Aerodynamic Noise from Vehicles."
Project P4 of the Ministry of Science and Technology
Ref: DPI2000-0431-P4-03
Duration: 2001-2004

9- "AEROSIVE: Interior noise prediction due to aerodynamic loading on vehicles: aircraft and high-speed trains."
CIDEM Project of the Generalitat de Catalunya
Ref: RDITCRD04-0074
Duration: 2004

10- "Metallic acoustic material"
CIDEM Project of the Generalitat de Catalunya
Ref: RDITCRD05-1-0010
Duration: 2005

11- "Development of new acoustic materials"
CIDEM Project of the Generalitat de Catalunya
Ref: RDITCINNN05-1-0023
Duration: 2005

12- "SAERVE: Evaluation and improvement of computational prediction of aerodynamic noise generated by vehicles."
CIDEM Project of the Generalitat de Catalunya
Ref: RDITCRD05-1-0010
Duration: 2005

13- "FOTACU: Development of acoustic photography technique"
CIDEM Project of the Generalitat de Catalunya
Ref: RDITSIN06-1-0211
Duration: 2006-2007

A LIST OF PRIVATELY FINANCED RESEARCH PROJECTS

1- "Cabin noise reconstruction at the mid-high frequency range"
Company: Ferrari Auto (Italy)
Duration: 1998

2- META X: Advanced vibroacoustic analysis in railways. Application of the GTDT method ".
Company: Alstom Transport (France)
Duration: 2001-2004

3- "ORNVS-ATPA: OROS NVGate Solution-Advanced Transfer Path Analysis"
Company: OROS (France)
Duration: 2003-2005

4- "Acoustic Blockage Detection Project"
Company: ENI Tecnologie (Italy)
Duration: 2003-2004

5- "META W: Advanced vibroacoustic analysis in railways. New technologies and calculation methods. Phase I."
Company: Alstom Transport (France)
Duration: 2004-2005

6- META W: Advanced vibroacoustic analysis in railways. New technologies and calculation methods. Phase I."
Company: Alstom Transport (France)
Duration: 2006

7- EVS: Equipments Vibration Specification": design and development of a tool specifying maximum noise and vibration levels for railway equipment to be installed on the train.
Company: Alstom
Duration: 2010 - 2012

8- "VITRASO: Diagnosis and prediction of noise transmission pathways in buildings."
Company: Fomento de Construcciones y Contratas
Duration: 2010 - 2011

9- Project "Inventory of Operational Modal Analysis (OMA)": determination of the own modes of the wind turbines in an automated way from measurements with the wind turbines in operation. Creation of a specific software customized for the client.
Company: Ecotecnia Energías Renovables
Duration: 2011-2012

10-SOME-ECO (Sound Meteorological Environmental Correlation) Project.
Duration: 2012-present

Acoustic photography is a technique for locating acoustic noise sources that can be applied quickly and effectively in any type of environment (including reverberants). Its name is due to the fact that it allows direct visualization of the position and power of the noise sources present in the study area under consideration. The reconstruction of the image is based on information obtained in the time domain from a large number of correlation functions measured by means of a microphone network.
ICR has participated in the development of codes and methods to implement the methodology in large microphone networks, while extending its use in the field of vibrations, in order to locate noise and vibration sources of unknown origin through accelerometer networks.