Assessment criterion for indoor noise disturbance in the presence of low frequency sources

Several studies have presented the effects of environmental noise in and around buildings and communities in which people live and work. In particular, the noise introduced into a building is mostly evaluated using the A weighted sound pressure level (LAeq) as the only parameter to determine the perceived disturbance. Nevertheless, if noise is produced by activities or sources characterised by a low frequency contribution, the measurement of LAeq underestimates the real disturbance, in particular during sleeping time. The international literature suggests methods to evaluate the low-frequency noise contribution to annoyance separately from the A weighted sound pressure level; almost all of the proposed methods are based on exceeding a threshold limit. This paper tests international criteria, by applying them in real-life indoor noise situations, and then analysing, comparing and contrasting results. Based on the result of the procedure above, a new criterion consisting of a single threshold is proposed, which simplifies the procedures in case of low-frequency components, but could be used for any situation

Results from On-The-Ground Efforts to Promote Sustainable Cattle Ranching in the Brazilian Amazon

Agriculture in Brazil is booming. Brazil has the world’s second largest cattle herd and is the second largest producer of soybeans, with the production of beef, soybeans, and bioethanol forecast to increase further. Questions remain, however, about how Brazil can reconcile increases in agricultural production with protection of its remaining natural vegetation. While high hopes have been placed on the potential for intensification of low-productivity cattle ranching to spare land for other agricultural uses, cattle productivity in the Amazon biome (29% of the Brazilian cattle herd) remains stubbornly low, and it is not clear how to realize theoretical productivity gains in practice. We provide results from six initiatives in the Brazilian Amazon, which are successfully improving cattle productivity in beef and dairy production on more than 500,000 hectares of pastureland, while supporting compliance with the Brazilian Forest Code. Spread across diverse geographies, and using a wide range of technologies, participating farms have improved productivity by 30–490%. High-productivity cattle ranching requires some initial investment (R$1300–6900/ha or US$410–2180/ha), with average pay-back times of 2.5–8.5 years. We conclude by reflecting on the challenges that must be overcome to scale up these young initiatives, avoid rebound increases in deforestation, and mainstream sustainable cattle ranching in the Amazon

Inter-comparison of laboratory measurements of dynamic stiffness

The AIA (Italian Acoustic Association) carried out an Inter-Laboratory Test (ILT) to evaluate the repeatability and the reproducibility of dynamic stiffness measurements of materials used under floating floors in dwellings, according to the ISO 9052-1 standard. The main target of the ILT was to quantify the measurement uncertainty among different laboratories due to the flexibility in the test procedures described in the standard. The obtained results, show that different factors, such as: the measurement set-up, the application of a thin paste on the test specimen, the pre-load time, the determination of the resonant frequency dependence by the excitation force amplitude and the enclosed gas dynamic stiffness definition may affect the results of the measurement to varying degrees, depending on the material typology. Considerations on measurement procedures and proposals for an integration of the standard are reported

Il comportamento acustico di edifici realizzati con struttura X-Lam

Gli edifici leggeri in legno stanno diventando una soluzione sempre più presente nel- la realtà costruttiva italiana. Questi posseggono indubbie doti di facilità di allestimento di cantiere e di velocità realizzativa. Inoltre, l’industrializzazione molto efficiente del processo di produzione ha ridotto i rischi di errori di progetto e di posa in opera. Le tipologie costruttive di questo tipo constano principalmente di due modelli: a te- laio (blockhouse, platformeframe, baloonframe), oppure a parete piena portante. La se- conda tecnologia contiene la parete prefabbricata di tipo X-LAM, dove pannelli di legno lamellare vengono uniti per formare pareti o solai con caratteristiche portanti, introdu- cendo problematiche progettuali in fase di previsione dei requisiti acustici passivi degli edifici. In questo lavoro, viene affrontata una prima disamina delle prestazioni di tali struttu- re al grezzo, con particolare focalizzazione ai risultati ottenuti con specifiche prove in opera. Queste hanno indagato il comportamento vibro-acustico di strutture orizzontali con diverse tipologie di connessioni. I risultati dimostrano come un procedimento indu- striale di produzione in serie e una progettazione per il collocamento dei vari pannelli comporti una costanza di prestazioni fornite anche col variare delle dimensioni e dei giunti