Laboratory of Acoustics and Mechanical Engineering
LEAM specialises in noise and vibration control techniques
in industry and government.
Its main areas of expertise are as follows:
Measurements with microphone antennas
A microphone array or antenna is a device consisting of a set of microphones carefully arranged throughout a space to measure the entire acoustic field simultaneously. This method can locate the acoustic sources of the sound generated and calculate the contribution made by each one. The spatial arrangement of the microphones can be linear, 2D or 3D, depending on whether one, two or three coordinates are required to identify the position of the acoustic sources.
Environmental noise management
LEAM characterises the noise generated in urban and non-urban spaces. There is a clear correlation between sound (or noise) and human activity. We can therefore expect the repetition of certain phenomena, which can be used to establish a framework for assessment and action in the area of sound (such as the acoustic preservation of natural spaces) or noise. Long-term measures for evaluating noise levels throughout the day are therefore an important tool for establishing the ambience of areas at night. LEAM also works on sound rating, since it has been found that equivalent level and A-weighting, which are used in most regulations, are not suitable for analysis in all situations, with the correlation between these parameters and the inconvenience caused not always being optimal.
Control of noise emissions
First, the noise sources are identified. Next, the influence of these sounds on noise emissions is analysed and determined. Finally, strategies are created to monitor and reduce the noise emissions produced by a product.
Active noise control
Active noise control is a technique that aims to reduce unwanted noise using electronically generated destructive interference with an additional (secondary) acoustic field.
Vibration and acoustic impact of infrastructure
Acoustic impact: Based on in situ noise measurements, the computer model used to analyse the affected area is validated. A study is then carried out in collaboration with environmental consultants, government bodies, etc., to identify the most appropriate corrective measures to reduce the size of the affected area or, if appropriate, the size of the affected population. Vibration impact: There is currently no standard procedure to characterise the vibrations caused by different sources (for instance, trains) or to characterise how the vibrations spread out. LEAM is currently working on developing and modelling the propagation of vibrations with different source–receiver configurations and different types of terrain. The centre hopes to use this to define a systematic procedure for predicting the impact of vibrations caused by infrastructure.
Acoustic quality in buildings
This involves reducing the noise generated by domestic facilities, such as sanitary facilities, lifts and air-conditioning systems, to make homes more comfortable.
This involves reducing the noise generated by domestic facilities,
such as sanitary facilities, lifts and air-conditioning systems,
to make homes more comfortable.
Companies that design and manufacture products in which low acoustic emissions provide an added value, and companies with noisy manufacturing processes or large industrial sites.
Cars, buses, airports, trains and vehicles in general.
Problems of isolation, noise caused by installations, acoustic impact and identifying corrective measures.
Support for environmental noise management; acoustic maps, plans and solutions to reduce noise and the acoustic and vibration impact of activities; and establishing methodologies and controlling the acoustic impact of major infrastructure (roads, airports etc.).
LEAM is a technological innovation centre that is part of the Department of Mechanical Engineering at the Universitat Politècnica de Catalunya.
Application of the active noise control technique to the cooling systems of wind turbines
In this study, the active control system consisted of a microphone and a loudspeaker. The main objective was to analyse the feasibility of using such a system and to find the best location for the two transducers to reduce the noise outside the duct.
Application of the active noise control technique to enable ventilation, but not sound, to pass through windows
The main objective was to reduce the level of noise heard inside a bedroom from aeroplanes taking off at a nearby airport when the bedroom window is left open. The active control system consists of a line of loudspeakers placed outside the window, various error microphones placed at the opening of a tilt-and-turn window, a reference microphone placed outside the house and a DSP. This project analysed how sound enters the house through the window and looked at the viability of applying the active control system and the system’s limitations. Using a loudspeaker and an error microphone, the active control system has reduced the level of noise inside the house by 2 dB.
Development of a system to automatically discriminate between aircraft noise and urban noise
Currently, one of the problems with the systems used to monitor aircraft noise is interference from urban noise generated by traffic and other sources. The purpose of this project was to design a microphone antenna that is able to distinguish between aircraft noise and urban noise. The 3 m antenna must be set up on the highest building in an area and can reduce the influence of urban noise on the measurements of aircraft noise by up to 6 dB.
Development of systems to identify the location and nature of noise sources
Various projects have been undertaken to distinguish and measure the acoustic level of specific noise sources in the presence of other noise sources. One of these projects determined the acoustic level of the pantograph of a high-speed train, distinguishing this noise source from other sources. Another project located and quantified the aerodynamic noise sources on the blades of a wind turbine. Linear microphone antennas were used in both projects.