Machine learning-based tools for wind turbine acoustic monitoring

The identification and separation of sound sources has always been a difficult problem for acoustic technicians to tackle. This is due to the considerable complexity of a sound that is made up of many contributions at different frequencies. Each sound has a specific frequency spectrum, but when many sounds overlap it becomes difficult to discriminate between the different contributions. In this case, it can be extremely useful to have a tool that is capable of identifying the operating conditions of an acoustic source. In this study, measurements were made of the noise emitted by a wind turbine in the vicinity of a sensitive receptor. To identify the operating conditions of the wind turbine, average spectral levels in one-third octave bands were used. A model based on a support vector machine (SVM) was developed for the detection of the operating conditions of the wind turbine; then a model based on an artificial neural network was used to compare the performance of both models. The high precision returned by the simulation models supports the adoption of these tools as a support for the acoustic characterization of noise in environments close to wind turbines

A comparison between numerical simulation models for the prediction of acoustic behavior of giant reeds shredded

Giant reeds represent a natural fiber widely available in some areas of the world. Its use can be particularly useful as the uncontrolled growth of giant reeds can be a problem because large areas are invaded by them and the crops are damaged. In this study, two models of numerical simulation of the acoustic behavior of giant reeds were put in comparison: the Hamet model and a model based on artificial neural networks. First, the characteristics of the reeds were examined and the procedures for the preparation of the samples to be analyzed were described. Then air flow resistance, porosity and sound absorption coefficient were measured and analyzed in detail. Finally, the results of the numerical modeling of the acoustic coefficient were compared. The neural network-based model showed high Pearson correlation coefficient value, indicating a large number of correct predictions

On the Validity of Immersive Virtual Reality as tool for multisensory evaluation of urban spaces

The Europe2020 document indicates a new strategy to turn EU into a smart, sustainable and inclusive economy. At local level urban planning policies may help to reach these aims. Several research works proposed the Immersive Virtual Reality as tool to evaluate the effectiveness of these interventions. Nevertheless people's perception within virtual environments still needs to be verified. In this study, two groups of participants had to provide subjective measures related to the global, acoustic and visual quality of a real environment or of a multisensory reproduced version in Immersive Virtual Reality. Outcomes highlight the ecological effectiveness of this multisensory tool

Towards the integration of urban sound planning in urban development processes: the study of four test sites within the SONORUS project

Noise pollution in urban environments is today a major problem affecting inhabitants of many European cities. Reducing noise is therefore a necessity. As a result, many cities now have noise action plans comprising concrete actions to tackle noise issues in affected areas. Nevertheless, these often isolated documents only address existing problems. In order to change this practice an integrated strategy is necessary. A new approach to urban sound planning, a holistic approach, is being developed and tested within the SONORUS project and it is described in this paper. SONORUS, the Urban Sound Planner project, is an initial training network (ITN) that is educating researchers in a whole range of acoustic disciplines, as well as in advanced urban planning processes. An essential part of this training is the application of the holistic approach to real test sites. Although this is an ongoing work, a few innovative techniques were already developed and its application to the test sites resulted in improved urban sound planning tools. This paper promotes the discussion about the implications that the holistic approach might have in urban sound planning policies and how it can be a driving force for changing the noise pollution situation in urban environment

Corn plants as temporary acoustic barrier to limit the effects of noise pollution

Corn is a cereal imported into Europe from the Americas. It is used for human and animal feed, but there are also industrial uses such as the production of ethanol, of fuel for heating homes, or the production of starch. Corn grows in the summer in areas where there is water. It is grown in many regions of the world and its production exceeds that of any other cereal in quantity. The corn plant can reach up to three meters in height, with a stem diameter of a few centimeters and with dense leaves longer than 30 cm and 10 cm wide. There are noisy activities where it is necessary to attenuate the noise produced to limit the effects of noise pollution. Some activities use temporary barriers depending on the processing cycle adopted. If noisy work is carried out during the summer season, corn rows of adequate width can be used as an acoustic barrier. In this paper, the possibility of using corn plants as an acoustic barrier is investigated. Acoustic measurements of the noise attenuation of corn rows of adequate width are described. Using a semi-spherical source placed on the ground, the acoustic attenuation due to the corn plants arranged in several rows for different distances from the sound source to the receiver was measured

Design Optimization of Three-Layered Metamaterial Acoustic Absorbers Based on PVC Reused Membrane and Metal Washers

Waste management represents a critical issue that industrialized countries must necessarily deal with. Sustainable architecture involves the reuse of materials with the aim of significantly reducing the amount of waste produced. In this study, a new layered membrane metamaterial was developed based on three layers of a reused PVC membrane and reused metal washers attached. The membranes were fixed to a rigid support, leaving a cavity between the stacked layers. The samples were used to measure the sound absorption coefficient with an impedance tube. Different configurations were analyzed, changing the number of masses attached to each layer and the geometry of their position. These measurements were subsequently used to train a model based on artificial neural networks for the prediction of the sound absorption coefficient. This model was then used to identify the metamaterial configuration that returns the best absorption performance. The designed metamaterial behaves like an acoustic absorber even at low frequencies

Evaluation of the injection moulding conditions in soy/nanoclay based composites

International audienceBiocomposites, and generally bio-based plastics, are seen as a promising alternative to conventional plastics because they are based on renewable natural components (eco-friendly) with a lower cost. Biocomposites using soy protein and glycerol were obtained with an injection moulding technique as the thennoprocessing method. Nanoclay (Montmorillonite, MMT-Na+) was included to improve physicochemical properties of novel SPI/MMT nanocomposites prepared by injection moulding, primary attending to water uptake capacity (WUC), but also considering rheological and mechanical properties. The influence of processing conditions has been studied in order to assess the modifications taking place in the microstructure and properties of these nanocomposites. Addition of MMT-Na+ improves mechanical properties and WUC of SPI-based materials, depending on processing conditions. Injection pressure only exerts a slight enhancement of mechanical properties and WUC. However, an increase in mixing time leads to a relevant increase in WUC without impairing the mechanical properties of nanocomposites

The acoustics of ancient catacombs in Southern Italy

The catacombs, burial sites for early Christians, were constructed during the Roman Empire until the Christian religion was recognized in 313 AD. The catacombs were cementeries, which were organized according to precise rules and were dug into the ground on several levels, to occupy as little space as possible. The catacombs became places of worship as martyrs were buried in them. The catacombs were then abandoned with the barbarian invasions and the consequent construction of churches inside cities. The catacombs were rediscovered during the Renaissance period and became a place of renewed worship. In the present work, the acoustic characteristics of the catacombs of San Callisto in Rome, San Gennaro in Naples, and Vigna Cassia in Syracuse are discussed. The three selected catacombs differ by type of excavation and geometry. In particular, the catacombs of San Callisto are made of narrow corridors and small rooms; the catacombs of San Gennaro consist of large rooms with niches; the catacombs of Vigna Cassia are partly excavated in the tuff and partially occupy a disused aqueduct. The acoustic measurements were performed using an impulsive sound source. The description of the acoustic characteristics focuses on the reverberation time and the Speech Transmission Index. The results show that the reverberation time was always shorter than 1 second, confirming the reduced reverberation of these environments. Finally, the speech listening characteristics are particularly good, ensuring the suitable conditions for the prayer in these spaces

Representation of the soundscape quality in urban areas through colours

Noise mapping is a useful and widespread method to visualise various items like the exposure to noise pollution, statistics of affected population, different noise source contribution analysis, and it is also a useful tool in designing noise-control plans. Some researches have moved a step further, proposing maps to represent the people perception of the acoustic environment. Most of these maps use colours as mere tools to display the spatial variability of acoustic parameters. In this paper the colours associated by interviewed people to different urban soundscapes have been analysed, and the possibility of using meaningful colours to represent the soundscape quality in noise mapping has been examined. For this purpose, correspondence analysis was applied on the data collected from on-site interviews, performed in the waterfront of Naples and its surroundings. The outcomes show that in the pedestrian areas nearby the sea, the blue colour was often associated with the soundscape rating, whereas in the areas nearby the sea but open to road traffic the interviewees selected mainly the blue and grey colours. In the areas away from the sea, a wider selection of colours was observed: red and grey were predominantly selected in the areas open to road traffic and green, yellow and red in the green areas