An alternative Drum test method to UNECE Regulation 117 for measuring tyre/road noise under laboratory controlled conditions

Tyre/road sound emissions have been proved to be the main source of noise caused by road traffic when traveling at medium and high speeds (Sandberg and Ejsmont, 2002). Tyre/road noise has been widely studied among the last decades. However, an important part of this research has been focused, mainly, on track tests. Different track or road methods have been developed for measurement of tyre/road sound emissions. The most important ones are the Coast-By, the Close-Proximity, the Statistical Pass-By or the Controlled Pass-By methods. Among all of them, the Coast-By method has been raised in Europe as standard method concerning the approval of tyres with regard to tyre/road sound emissions as preconized in UNECE Regulation 117 (2007)[2]. However, all the above mentioned methods have several disadvantages such as the influence of environmental factors, the different results that can be obtained depending on the test track or the vehicle upon which the tests are carried out, the lack of repeatability or, the most important aspect, which is the limitation of the measured magnitude, the sound pressure level. A new methodology (Clar-Garcia et al., 2016) based on drum tests and the ISO 3744 (1994), which was developed in order to avoid these limitations, has been proved to be comparable to the Coast-By (CB) method. This paper describes how different tyres have been tested according to both the CB and the new Alternative Drum test method (A-DR) while their results have been compared. In order to be able to carry out this comparison, as the measured magnitudes and test conditions differ widely from one test to another, the standardised ISO 9613 sound propagation method (ISO 9613-2, 1996) has been applied to obtain the sound pressure value at 7.5 m from the sound power level of a tyre measured under laboratory-controlled conditions when rolling against a drum. Results have shown that both methods are not only comparable but also have remarkably similar sound spectra and, for that reason, the new methodology based on drum tests can be used in order to obtain tyre/road noise emission approved values

The evolution of the ventilatory ratio is a prognostic factor in mechanically ventilated COVID-19 ARDS patients

Background: Mortality due to COVID-19 is high, especially in patients requiring mechanical ventilation. The purpose of the study is to investigate associations between mortality and variables measured during the first three days of mechanical ventilation in patients with COVID-19 intubated at ICU admission. Methods: Multicenter, observational, cohort study includes consecutive patients with COVID-19 admitted to 44 Spanish ICUs between February 25 and July 31, 2020, who required intubation at ICU admission and mechanical ventilation for more than three days. We collected demographic and clinical data prior to admission; information about clinical evolution at days 1 and 3 of mechanical ventilation; and outcomes. Results: Of the 2,095 patients with COVID-19 admitted to the ICU, 1,118 (53.3%) were intubated at day 1 and remained under mechanical ventilation at day three. From days 1 to 3, PaO2/FiO2 increased from 115.6 [80.0-171.2] to 180.0 [135.4-227.9] mmHg and the ventilatory ratio from 1.73 [1.33-2.25] to 1.96 [1.61-2.40]. In-hospital mortality was 38.7%. A higher increase between ICU admission and day 3 in the ventilatory ratio (OR 1.04 [CI 1.01-1.07], p = 0.030) and creatinine levels (OR 1.05 [CI 1.01-1.09], p = 0.005) and a lower increase in platelet counts (OR 0.96 [CI 0.93-1.00], p = 0.037) were independently associated with a higher risk of death. No association between mortality and the PaO2/FiO2 variation was observed (OR 0.99 [CI 0.95 to 1.02], p = 0.47). Conclusions: Higher ventilatory ratio and its increase at day 3 is associated with mortality in patients with COVID-19 receiving mechanical ventilation at ICU admission. No association was found in the PaO2/FiO2 variation

Metodología de ensayo en laboratorio para la medición del ruido de rodadura de neumáticos

La interacción neumático/carretera es la principal fuente de emisión de ruido causado por el tráfico rodado cuando se circula a velocidades de más de 30 km/h y de menos de 120 km/h, a partir de la cual, el ruido aerodinámico empieza a predominar. Varios métodos tales como el Coast-By, el Close-Proximity, el Statistical Pass-By o el Controlled Pass-By se han utilizado durante las últimas décadas para medir la emisión de ruido. Sin embargo, desde que se publicó el Reglamento (CE) No 1222/2009 del Parlamento Europeo y del Consejo de 25 de noviembre de 2009 sobre el etiquetado de los neumáticos en relación con la eficiencia en términos de consumo de carburante y otros parámetros esenciales, solo el método descrito en el Reglamento 117 de la Comisión Económica para Europa de las Naciones Unidas (CEPE) Disposiciones uniformes relativas a la homologación de neumáticos por lo que se refiere a las emisiones de ruido de rodadura, a la adherencia en superficie mojada y/o a la resistencia a la rodadura, puede ser usado con la finalidad de obtener valores aceptados de emisión sonora para el ruido de rodadura. Todos estos métodos convencionales tienen varias desventajas y limitaciones tales como la falta de repetibilidad, la influencia de factores ambientales o los diferentes resultados que pueden ser obtenidos dependiendo de la pista de ensayo o del vehículo con el cual se lleven a cabo los ensayos. Hace falta, por tanto, una metodología de ensayo que sea capaz de eliminar o reducir todas las desventajas enumeradas anteriormente y mediante la cual la medida del ruido de rodadura sea más rápida, fiable y económica. La presente Tesis Doctoral desarrolla un nuevo método de ensayo para la obtención del nivel de potencia sonora que emite un neumático en banco de ensayos tipo Drum basándose en la norma internacional ISO 3744. Este nuevo enfoque combina la experiencia del método ISO con el procedimiento experimental desarrollado en las instalaciones de ensayo de neumáticos del Laboratorio de Vehículos de la Universidad Miguel Hernández de Elche. La novedad radica en que ninguno de los grupos de investigación que ha ensayado el ruido de rodadura de neumáticos usando tambores lo ha hecho por medio de un método de ingeniería específico estandarizado para determinar el nivel de potencia acústica. Por el contrario, todas las pruebas anteriores han considerado únicamente la presión sonora que es una magnitud que depende de factores tales como el medio en el que viajan las ondas sonoras, la atenuación o la distancia de la fuente sonora por lo que mediante la medición de la presión sonora no es posible cuantificar la potencia del sonido de la fuente a menos que todos y cada uno de los factores anteriormente mencionados estén estrictamente controlados y definidos, hecho que no sucede totalmente en la metodología descrita en el Reglamento 117. Esta nueva metodología para realizar los ensayos en laboratorio tipo Drum, incluye la localización de los micrófonos, la obtención de los factores de corrección por ruido de fondo y por entorno acústico de ensayo y el procedimiento operativo para la medición de la presión sonora y la obtención de la potencia sonora que emite el neumático. El nuevo método ha sido validado mediante la comparación con los resultados obtenidos en numerosos ensayos en pista realizados siguiendo el método Coast-By descrito en el Reglamento 117 y utilizando el modelo de propagación sonora descrito en la norma ISO 9613, mediante el cual ha sido posible obtener el nivel de presión sonora que se obtendría en el ensayo en pista a partir del nivel de potencia sonora obtenido en el laboratorio de ensayo. Los resultados obtenidos en la presente Tesis Doctoral permiten concluir que se ha logrado el objetivo principal de la investigación, obteniendo un método de ensayo en laboratorio válido para evaluar el ruido de rodadura en ensayo de homologación de neumáticos.Tyre/road interaction is the main source of noise emission caused by road traffic when cruising at speeds over 30 km/h and less than 120 km/h, from which aerodynamic noise begins to predominate. Several methods such as the Coast-By, the Close-Proximity, the Statistical Pass-By or the Controlled Pass-By have been used over recent decades to measure noise emission. However, since Regulation (EC) No 1222/2009 on the labelling of tyres was published, only the method described in UNECE Regulation 117 concerning the approval of tyres with regard to rolling sound emissions, can be used in order to obtain tyre/road noise emission approved values. All these conventional methods have several disadvantages and limitations such as the lack of repeatibility, the influence of environmental factors or the different results that can be obtained depending on the test track or the vehicle upon which the tests are carried out. The lack of a new methodology that eliminates or reduces all the disadvantages listed before and by which tyre/road noise measurement is done on a faster, more reliable and cheaper way, is obvious. This Doctoral Thesis has developed a new test method for obtaining sound power level emitted by a tyre in a Drum facility based on the international standard ISO 3744. This new approach combines the expertise of the ISO method with the experimental procedure developed in the tyre test facilities of the Vehicle Laboratory at Universidad Miguel Hernández de Elche. The innovation is that none of the research groups that have tested the tyre rolling noise using drums have done it by a specific engineering standardized method for determining the sound power level. On the contrary, all previous tests have considered only sound pressure, which is a magnitude that depends on factors such as the medium in which sound waves travel, the attenuation or the distance from the sound source so by measuring the sound pressure is not possible to quantify the sound power of the source unless each and every one of the above mentioned factors are strictly controlled and defined, a fact not entirely true on the methodology described in Regulation 117. This new methodology for tests in Drum facilities includes the location of microphones, obtaining correction factors for both background noise and acoustic environment and the operational method for measuring sound pressure and obtaining the sound power emitted by the tyre. The new method has been validated by comparison with the results of several track tests carried out according to the Coast-By method described in Regulation 117 and using the sound propagation model described in ISO 9613 standard, which allows to get the sound pressure level to be measured at the test track from the sound power level obtained in drum facilities. The results obtained in this Doctoral Thesis can conclude that the main goal of the research has been achieved, obtaining a valid test method for measuring tyre-rolling sound emission for approval of tyres