Category Archives: Research

Modelling sound absorption properties of broom fibers using artificial neural networks

he use of broom to produce fibers has ancient roots. The Greeks appreciated its resistance to water and for this reason they used it to manufacture sailing ropes. But broom fiber was also appreciated for its sound absorption qualities. In this study, a new methodology was developed for the numerical modeling of the acoustic behavior of broom fibers. First, the characteristics of the different varieties of broom were examined and the procedures for processing the samples to be analyzed were described. Subsequently, the results of the measurements of the following acoustic properties of the material were analyzed: air flow resistance, porosity, and sound absorption coefficient. Finally, the results of the numerical modeling of the acoustic coefficient were reported using an algorithm based on artificial neural networks. The results obtained are compared with a model based on linear regression.

Case study: Automated recognition of wind farm sound using artificial neural networks

Wind energy has been one of the most widely used forms of energy since ancient times, with it being a widespread type of clean energy, which is available in mechanical form and can be efficiently transformed into electricity. However, wind turbines can be associated with concerns around noise pollution and visual impact. Modern turbines can generate more electrical power than older turbines even if they produce a comparable sound power level. Despite this, protests from citizens living in the vicinity of wind farms continue to be a problem for those institutions which issue permits. In this article, acoustic measurements carried out inside a house were used to create a model based on artificial neural networks for the automatic recognition of the noise emitted by the operating conditions of a wind farm. The high accuracy of the models obtained suggests the adoption of this tool for several applications.

Wind turbine noise prediction using random forest regression

Wind energy is one of the most widely used renewable energy sources in the world and has grown rapidly in recent years. However, the wind towers generate a noise that is perceived as an annoyance by the population living near the wind farms. It is therefore important to new tools that can help wind farm builders and the administrations. In this study, the measurements of the noise emitted by a wind farm and the data recorded by the supervisory control and data acquisition (SCADA) system were used to construct a prediction model. First, acoustic measurements and control system data have been analyzed to characterize the phenomenon. An appropriate number of observations were then extracted, and these data were pre-processed. Subsequently two models of prediction of sound pressure levels were built at the receiver: a model based on multiple linear regression, and a model based on Random Forest algorithm. As predictors wind speeds measured near the wind turbines and the active power of the turbines were selected. Both data were measured by the SCADA system of wind turbines. The model based on the Random Forest algorithm showed high values of the Pearson correlation coefficient (0.981), indicating a high number of correct predictions. This model can be extremely useful, both for the receiver and for the wind farm manager. Through the results of the model it will be possible to establish for which wind speed values the noise produced by wind turbines become dominant. Furthermore, the predictive model can give an overview of the noise produced by the receiver from the system in different operating conditions.

Fault diagnosis for UAV blades using artificial neural network

In recent years, unmanned aerial vehicles (UAVs) have been used in several fields including, for example, archaeology, cargo transport, conservation, healthcare, filmmaking, hobbies and recreational use. UAVs are aircraft characterized by the absence of a human pilot on board. The extensive use of these devices has highlighted maintenance problems with regard to the propellers, which represent the source of propulsion of the aircraft. A defect in the propellers of a drone can cause the aircraft to fall to the ground and its consequent destruction, and it also constitutes a safety problem for objects and people that are in the range of action of the aircraft. In this study, the measurements of the noise emitted by a UAV were used to build a classification model to detect unbalanced blades in a UAV propeller. To simulate the fault condition, two strips of paper tape were applied to the upper surface of a blade. The paper tape created a substantial modification of the aerodynamics of the blade, and this modification characterized the noise produced by the blade in its rotation. Then, a model based on artificial neural network algorithms was built to detect unbalanced blades in a UAV propeller. This model showed high accuracy (0.9763), indicating a high number of correct detections and suggests the adoption of this tool to verify the operating conditions of a UAV. The test must be performed indoors; from the measurements of the noise produced by the UAV it is possible to identify an imbalance in the propeller blade.

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.

Noise Exposure of PC Video Games Players

Video games are a leisure activity that is being practiced by more and more people. Even the average age of the users is gradually increasing, representing a pleasant activity for any age. The literature has widely insinuated the doubt whether such widespread use could have negative consequences for the health of its users. This article describes noise exposure measurement activities for video game users. The damage caused by noise depends on both the acoustic power as well as the exposure time. For this reason, different noise exposure scenarios produced by video games have been simulated. The results of the study show that the daily level of noise exposure is close to the limits imposed by legislation, despite the hours of rest, and were performed in an environment with a low background noise (46.0 dBA).

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Heating, Ventilation, and Air Conditioning (HVAC) Noise Detection in Open-Plan Offices Using Recursive Partitioning

Open-plan offices have lower construction costs, allowing for significant savings in space and, according to designers, facilitate communication between workers, thus, improving collaboration, as well as the exchange of ideas. For these reasons, this type of office has become widespread, while highlighting numerous limitations and various problems. These include the control of anthropic and electromechanical noise. In this study, measurements of the noise emitted by a heating, ventilation, and air conditioning (HVAC) system were carried out in an open-plan office. The average spectral levels in a 1/3 octave band were compared through correlation analysis, to identify any redundant data. A model was then adapted to evaluate the importance of the variables, in order to classify the characteristics, by importance. To reduce the number of predictor variables, a selection analysis of the characteristics was carried out. A subset of predictors was extracted to be used to produce an accurate prediction model. Finally, a model based on recursive partitioning, to detect the operating conditions of an HVAC system, was developed and applied, so as to provide insights into the development and application of this technique, in these contexts. The high accuracy of the model (Accuracy= 0.9981) suggests the adoption of this tool for several applications.

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Esposizione al rumore degli arbitri non professionisti

arbitriNegli ultimi anni l’attenzione posta dai ricercatori e dagli enti di controllo, nei confronti di attività lavorative di settori non industriali in cui possono sussistere potenziali rischi di esposizione al rumore, come quello scolastico e della musica, ha messo in evidenza come anche nell’ambito di attività di carattere prevalentemente antropico, possano determinarsi condizioni di esposizione al rumore critiche per la salute dei soggetti interessati.

Nell’ambito di queste attività, l’esposizione al rumore degli arbitri di competizioni sportive indoor, con particolare attenzione per la categoria degli arbitri “non professionisti”, merita un particolare interesse. Ciò è dovuto principalmente a due diversi aspetti: uno legato all’entità e tipologia dell’esposizione al rumore; l’altro alla natura extralavorativa e volontaria della prestazione svolta.

Dalle poche ricerche effettuate in questo settore è emerso che, già sugli spalti dei palazzetti, durante lo svolgimento di manifestazioni sportive, i livelli di rumore sono mediamente compresi tra 90 e 100 dB(A) con livelli di picco fino a 138,3 dB(A) [6]. Relativamente all’esposizione degli arbitri Flamme e Williams [7], in uno studio basato sull’autovalutazione dello status del proprio udito e sull’influenza dell’uso dei fischietti, hanno rilevato che, circa il 48% dei giudici di gara appartenenti al MHSA (Michigan High School Athletic Association) dichiaravano di aver avuto un acufene dopo aver arbitrato durante l’ultimo anno, il 13% quasi sempre e l’11% per più di una volta alla settimana o più di una volta al mese.


Nello stesso studio, gli autori, hanno misurato, per 13 diversi modelli di fischietti, valori del SELA,FF ad 1 metro compresi tra 104 e 116 dB(A), con frequenze di picco tra 3 e 4 kHz. Dal punto di vista degli effetti sugli arbitri, Smith [8] ha misurato l’innalzamento temporaneo della soglia uditiva pre e post gara per alcune competizioni di basket rilevando, alla frequenza di 4kHz, innalzamenti medi tra le due orecchie di circa 22,5 dB.

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Esposizione al rumore degli arbitri non professionisti

Noise and meteorological monitoring of a wind farm


Wind energy is one of the cleaner and more environmentally friendly of renewable energy, nevertheless the installation sites of Wind Farms (WF) must comply with different requirements (e.g. wind speed and direction, absence of obstacles, distances to dwelling). Mountain ridges and hills sites far from urban centre fulfil these requirements and were the firsts to be occupied by WF. However, the continuous increase of wind energy systems has implied that even more portions of territory were involved by the WF installation.

Moreover rather than their high level of environmental compatibility to others energy plants, a public resistance toward WF is frequently encountered. The motivations ascribed to the opposition are mainly connected to physical (noise and visual impact) and individual aspects (green energy or wildlife preservation attitude, degree of involvement in the project, economic benefits, NIMBY).


The methodologies for noise assessment of WF at the receiver points are rather standardized and widely described by national legislations. Two methods are generally used. These methods assess the WF noise contribution from the measurements of the Combined Noise Level and of the Background Noise Level.

In the first method, the measurements must be carried out in two different temporal stages: when the wind turbines (WTs) are working and then, immediately after the time that the WTs are parked.


In this way the background noise may be assessed, assuming that the measurements are recorded under the same weather conditions (remaining unchanged between these short time intervals). Subtracting the Background Noise Level from the Combined Noise Level it is possible to obtain the contribution of the WTs noise. Moreover some legislation recommend to measure the Background Noise Level “prior to site construction and operation” with a long-term measurement survey .

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Noise and meteorological monitoring of a wind farm

Monitoraggio e mappatura acustica delle strade provinciali della Provincia di Napoli

provLa realizzazione di mappature acustiche rappresenta, ad oggi, il principale strumento per la caratterizzazione acustica ambientale e per la gestione dei territori in relazione all’inquinamento acustico. Attraverso l’utilizzo di software commerciali di modellazione acustica per ambienti esterni è possibile stimare i livelli prodotti in specifici punti ricevitore o realizzare mappature, a partire da dati caratterizzanti le sorgenti acustiche (traffico veicolare, ferroviario, aeroportuale o da sorgenti industriali).

Tuttavia, nell’ambito della procedura di redazione delle mappature acustiche per la redazione dei Piani di Contenimento previsti dal D.M.A. 29/11/2000 risulta estremamente delicata la fase di utilizzo dei dati rilevati in situ per la calibrazione del modello acustico implementato nei suddetti software. Allo stesso tempo, la fase di calibrazione risulta di particolare interesse dato che gli standard proposti dalla direttiva 2002/49/CE portano ad un errore generale in particolare riguardo al modello di emissione a causa del fatto che sono riferiti a database delle emissioni particolarmente datati.

Nel seguito viene descritta una procedura di misura e calibrazione/validazione del modello acustico ispirata alla norma UNI 11143, parti 1 e 2 [3, 4]. La procedura ha previsto una prima fase di scelta delle strade oggetto di monitoraggio, tale scelta è stata effettuata in modo da formare un database di tipologie stradali omogenee secondo emissione e propagazione acustica tali da coprire le diverse tipologie presenti sul territorio di studio.


Per ogni strada è stata scelta una sezione rappresentativa in cui effettuare il monitoraggio fonometrico e dei flussi di traffico. In ogni sezione oggetto di monitoraggio sono stati effettuati rilievi fonometrici di lunga durata in corrispondenza del ricettore abbinati a misure in prossimità della sorgente ed a rilievi spot a distanza crescente dall’infrastruttura. Le rilevazioni fonometriche sono state accompagnate da rilievi dei flussi di traffico per permettere la taratura del modello acustico e la determinazione dei fattori correttivi per i modelli di emissione e propagazione.

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Monitoraggio e mappatura acustica delle strade provinciali della Provincia di Napoli

Realizzazione di un data base per le proprietà acustiche di materiali ecocompatibili


Ai materiali ecocompatibili appartengono i prodotti di origine naturale (animale, vegetale o minerale) ovvero di non sintesi chimica che derivano da materiali rinnovabili, che non emettono sostanze inquinanti per l’ambiente e dannose per l’uomo, che sono riciclabili o biodegradabili e che richiedono un basso contenuto di energia per l’intero ciclo di vita.

I materiali ecocompatibili si stanno diffondendo nel settore dell’edilizia e sono impiegati anche per la correzione acustica di ambienti. Sul mercato sono disponibili diverse tipologie di materiali (kenaf, canapa, sughero, lana di pecora, ….).  Per ciascuna tipologia è stata dapprima svolta un’attenta analisi della diffusione sul mercato.


Per ogni materiale individuato, sono state eseguite misure delle proprietà acustiche (coefficiente di assorbimento ad incidenza normale in un tubo ad impedenza e della resistenza al flusso dell’aria) in accordo con le vigenti norme UNI.

I risultati per ciascuna tipologia sono stati inseriti in un “data base” sia per esigenze di sintesi e consultazione, sia per semplificare la scelta da parte degli utenti. Il lavoro riporta le fasi di scelta del materiale, delle misure acustiche, della costruzione del “data base”; dell’inserimento delle informazioni “acustiche” nel “data base” e della relativa consultazione.

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Realizzazione di un data base per le proprietà acustiche di materiali ecocompatibili