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An effective program for external noise reduction of vehicles was firstly established in Brazil by an agreement between ANFAVEA and CETESB in the beginning of last decade. IBAMA worked this proposition and published in 1993 the first CONAMA Resolution, including the pass-by noise limits and the deadlines to satisfy the new sound pressure levels. Since then, CONAMA is responsible for this subject. In 2001 lower levels were imposed, similar to those existing in Europe, with 2006 as the deadline for all vehicle families. The paper describes and gives and overview of the procedures, the acoustic technologies and improvements developed to achieve, in two steps, the new limits, mainly for commercial vehicles, like heavy trucks {from 92 dB(A) to 80 dB(A)} and passenger cars {from 84 dB(A) to 74 dB(A)}. We enumerate also the non-acoustic problems solved, for instance the thermal problems, due to the acoustic barriers applied to reduce pass-by noise.

We present the physical concepts of acoustic barriers which have the purpose of reducing airborne sound transmission for both paths: internal and external noise. We introduce the mass-spring model, the utilization of compound sandwiches, and the improvement of the Transmission Loss through the use of channels in the material working as spring. We show some results regarding the behavior of absorption materials exposed to environment/working conditions. In addition we discuss the effect of acoustic leaks and the way of evaluating these barriers in vehicles. We show examples based on experimental investigations.

The paper presents the concepts and applications regarding Articulation Index (AI) that is widely used in the automotive industry as a powerful parameter to qualify/quantify the middle and high frequency spectra associated to the internal noise of vehicles. We are able to show a short historical review including the today used definitions and calculations based in third octave band spectra through and idealized speech region model like our pioneer Brazilian standard. We show also other applications, where AI can be an excellent tool to evaluate vehicle acoustics. We emphasize the relation of AI to Speech Intelligibility and make considerations concerning other factors influencing Intelligibility. In addition we comment the integration we have produced with an overall noise parameter like dB(A) - (H-index) and the proposition of an AIM - Articulation Index Modified.

The paper uses sets of experimental data, concerning commercial vehicles, to study the correlation between pass-by and stationary noises through measurements executed according to external noise standards. We consider two sets of experimental data: before the new legislation (higher levels) and lower levels satisfying the new limits in Brazil. In addition we calculate the Loudness in sones, from the octave band spectrum, and compare the results with the usual evaluation in dB(A), with the purpose of emphasizing the qualification besides the quantification aspects and promoting conditions for people understanding. We have applied Brazilian standards which are technically equivalent to their correspondent ISO 362 and ISO 5130. Some points regarding the application of these standard are in discussion since the last few years, as follows: The application of ISO 5130 in circulation vehicles and its correlation and meaning when compared to pass-by noise.

Due to the growing need of reducing development time of new products and also to evaluate their reliability, a growing trend towards reduction of field tests has been noted. Bench tests, in contrast, are being more widely used because of the reduced time to carry them out, at much lower costs. In the automotive industry this trend has led to great efforts to make these bench tests as truthful as possible in order to increase their reliability. The quantity of simulated parameters is growing and this, or course, requires the collection of an ever increasing quantity of data from signal measurements (acceleration, temperature, pressure, flow, etc.) in experimental vehicles.

Because of the increasing need to reduce the time of development of new products, or even to evaluate the reliability of products, one has been noticing a trend to rationalize field tests through essays in ever more representative test benches, within a shorter period of time at a lower cost. In the automotive industry, the trend is to increase the reliability of tests in benches. The quantity of simulated parameters is increasing, what demands an ever increasing survey of data based on measurements of signals of deformation of leaves of spring leaf and courses of suspension in experimental vehicles.

With the increasing necessity of reducing the development time of new products, and also the need to evaluate product reliability levels, a trend to rationalize field tests through test benches has been noted. These tests have proved more and more representative and carried out in much lower times and with lower costs. In the automotive industry this trend has generated considerable effort towards making these bench tests more representative of actual conditions towards the increase of their reliability. The quantity of simulated parameters is growing and it becomes necessary to collect more data from ground measurements signal (acceleration, temperature, pressure, flow, etc.) in experimental vehicles.

The paper describes the acoustic development effected in one middle-class commercial vehicle with the purpose of achieving the external sound pressure levels dictated by new Brazilian legislation. The philosophy adopted as well as the mandatory modifications of the truck to fulfill the noise limits are showed together with the non-acoustic characteristics. Besides the acoustic treatment of some specific sources, it was introduced an acoustic barrier, usually called capsule or shield to reduce the noise emission of the engine-transmission assembly working by the mass law principle and sound absorption.

Since the rising of the automotive industry, the concern with the driving itself has been the main task of the developments, which have improved the safety-related vehicle systems, such as headlamps and signalling devices that have received significant investments in technology. The paper deals with some functional and durability tests applied to illumination and signalling devices used in the automotive industry. We describe some durability tests like: vibrations, sealing tests, vehicles tests, …… emphasizing the research regarding headlights internal pressure variations relative to the protection against adverse environmental conditions. Concerning functional tests we focus those related to Photometry and Colorimetry, using Psychophysical parameters and the CIE International System XYZ (Commission International de l'Eclairage).

The interior noise of automotive vehicles is basically composed by two portions. The structureborne sound through the elastic moutings, which is characterized by the low frequencies and the airbornesound through the divisory between the engine compartment and passenger compartment. This last path is mainly traveled by the high frequencies. We show the low frequencies, specially those related to the explosion order make the composition of the overall sound level, when the noise is evaluated by a weighting curve, trying to simulated the ear response, as for example the curve “A”, from which originates the well familiar dB(A). The highest frequencies, although almost ever, are neglected by the weighting curve “A”, are very important when we see the communication aspect in the passenger compartment. To solve this, we use another parameter, calculated from physical measurements and named Articulation Index (Al). We show its association with the highest frequencies.

We are living an ecologic decade. The aspects concerning comfort and safety are emphasized, including also the commercial vehicles. The interaction between mass-machine-environment is very important. The acoustic comfort belongs to this context. This paper presents the acoustic development relative to the internal noise reduction of a road bus. The internal noise of automotive vehicles is composed by two parcels: the structureborne noise, which is characterized by the low frequencies and the airborne noise which arrives at the passenger compartment passing directly through the divisory between passenger compartment and engine compartment; this path is preferred by the high frequencies. In this work we present the technics we have applied to reduce noise coming from both paths. The quantification of the obtained results is elaborated through the measurements of sound pressure levels, specially the weighting curve “A” for the overall noise.

This paper goes beyond the usual Loudness and make the introduction of a new parameter called Perceived Magnitude, developed by Stevens, as an improvement to qualify/quantify acoustic sensations. As a pioneer application we have applied it to quantify some acoustic sources associated to automotive industry. We emphasize the differences concerning Loudness and Perceived Magnitude, and show the right way to compare the results. The sound pressure level spectra of some sources in octave bands are used to calculate the overall noise in SONES associated to the above parameters as well the usual dB(A). A suggestive and innovative spectral composition weighted by the above functions is introduced to interpret the results. Finally we discuss the benefits we can achieve using the new parameter in vehicle acoustics.

Competition in Automotive Market is driving the need for more time - and cost - effective testing methods. In the fatigue life analysis of new passenger and commercial vehicle designs, laboratory testing through servohydraulic equipment plays a very important role. In DaimlerChrysler do Brasil, the Durability Test Laboratory represents an important basis to assure high endurance reliability for all kinds of our commercial vehicle applications. In order to respond to the above mentioned testing tasks, this paper will focuse what we call our “New Policy of Durability Tests for Commercial Vehicles”, based on development of simple and low cost Road Simulators, fully dedicated and customized to testing of vehicle components and chassis. Experimental results as well as other data related to consumption of laboratory's: area, utilityes, pressurized hoses and test time, will be used in order to illustrate advantages and disadvantages of the new testing resource.

This paper discusses some aspects of durability tests in laboratory, justifying the necessity of a new procedure for data compression. Attention is paid to dynamic tests, with the presence of inertia forces. The new procedure is introduced, which uses concepts of fatigue due to vibration and signal analysis. The compression procedure is applied to generate a synthetic signal for the experimental stress test of an automotive component.

The paper looks for the degree of linear correlation of some acoustic parameters when their results are compared taking into consideration the internal noise of a set of passengers cars and another set of commercial vehicles. The acoustic parameters dealing with the overall noise (Loudness, dB(A) and dB(B)) and those related to the high frequency portion of the spectrum (Articulation Index and Sharpness) are chosen. The sound pressure levels in the passenger compartment are measured according to ISO 5128. The parameters are calculated in some specific velocities. A least square fit to a straight line to each pair of the acoustic parameters is applied. The results are discussed taking into consideration the degree of correlation trying to investigate how dependent or independent the parameters are. In addition it is possible to see the fluctuation range of these parameters concerning each set of vehicles.

This paper presents in a chronological way the main parameters used for automotive vehicles concerning acoustic qualification/quantification. We start with the loudness concept, pass by the “A” weighting philosophy and arrive to the sound level reduction including sound quality. We are able to show a lot of parameters, each one trying to match better the correlation between objective results and subjective evaluations. We mention several aspects regarding the human ear that make difficult the description of sound sensations through a single parameter. We emphasize also the absence of the exposure time in the parameters used to evaluate acoustic comfort. It is shown the large gap between the parameters used in lab and those applied in the legislations through some standards. Some conclusions are presented and the future related to acoustic parameters are discussed.

This paper uses sets of experimental data, concerning commercial vehicles, to study the correlation between pass by and stationary noises through measurements executed according to external noise standards. We consider two sets of experimental data: before the new legislation (higher levels) and lower levels satisfying the new limits in Brazil. In addition we calculate the Loudness in sones, from the octave band noise spectrum, and compare the results with the usual evaluation in dB(A), with the purpose of emphasizing the qualification besides the quantification aspects and promoting conditions for people understanding. Besides the overall noise, we show the bandwidth contribution for each parameter and analyse the spectrum profile associated to the “A” weighting curve applications. The discussions, conclusions and recommendations are supported by regression curves and graphics taken from the measurements effectuated involving the chosen parameters.

In order to attend the more demanding expectations of the commercial vehicles customers, it is being looked for improvements in order to reach better comfort on driving. Among the systems that interact with the driver, the shifting system can be distinguished. The development of a commercial vehicle shifting system is getting complex, because besides making possible the gear changes, it should follow comfort, ergonomics and durability parameters, balancing the necessary robustness for heavy applications with the shift smoothness desired by the user. At the start of the development of commercial vehicles shifting systems, the concept to be applied is analyzed, defining the model. Then it starts the study of the system construction, according to layout parameters of the vehicle project. This stage is predominantly accomplished by computer models. Then the prototypes are manufactured, in which functional tests are made for refinement.

Since the Weber-Fechner Law (1860) until 1950 there was no trustful method to calculate Loudness of complex sounds. At that time, ISO proposed three weighting curves, A, B and C based on rough approximations of the isophonic curves, 40, 70 and 100 phons. It was supposed to be a temporary suggestion. Curves B and C were abandoned, but A weighting survives until today! In 1957, Stevens and Zwicker presented two independent methods to obtain Loudness in sones, based on the new Stevens' Power Law. In 1965, Kryter introduced Noisiness in noys. Stevens in 1975 presented Perceived Magnitude as an improvement of Loudness calculation. In these acoustic parameters, the sound pressure levels per frequency band are transformed into acoustic sensation levels, and through the sensation spectrum the magnitude of the overall sensation is calculated. The A, B and C curves, for low, moderate and high levels do not follow this concept.