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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.

Recent studies in the USA show 2800 passenger casualties/year, due to automobiles and light vehicles impacting against the front structure of medium and heavy trucks at speeds over 45 mph. This same driver or passenger leaves the vehicle and becomes a pedestrian. What is being done in the automotive industry to face this situation? What improvements can be expected in automobiles, trucks and buses in the XXI century? The results obtained in this work show that it is possible and very important for new projects and modernization of commercial vehicles (trucks and buses) to introduce a front bumper concept foreseeing the Passive Safety of third parties (passenger vehicles).

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.

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.

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.

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.

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.

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.

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.

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.

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.

Vehicle Safety is very attractive, concerning active or passive safety. The collisions are intensively studied including deformations, kinematics, protections, devices and injuries. By the way, today we have a lot of computer programs trying to simulate these crash-tests. But, we can have an idea about the magnitude of the impact forces of a vehicle against a rigid wall starting from known physical concepts and simplified approximations. This is one of the purposes of this work. The classic problem of projectile impacts against a rigid wall and the example of an aircraft impact against a nuclear power plant are used to consider the models applied to vehicles. We consider the disacceleration of a material point and also the vehicle as an extense object. Real data are used to quantify the achieved expressions. We compare and discuss the magnitude of the forces, for instance, between a passenger car and a commercial vehicle.

The paper looks for the degree of linear correlation of some acoustic parameters concerning Speech Intelligibility in vehicles. The Articulation Index (AI) was originally a criterion to characterize the influence of parasite noise on the Intelligibility of a conversation in the design of speech communication systems. Introduced in the automobile acoustics, it is more and more commonly used by vehicles manufacturers to estimate the middle and high frequency content of spectra noise inside various types of vehicles driven under several running conditions. The correlation with Speech Intelligibility, measured through subjective measurements is well known. Presently we have more sophisticated parameters like STI, RASTI, SII… directed mainly to architectural acoustics and sometimes used in vehicle acoustics. They require specific hardwares and softwares and are more complicated to deal with and often are called machine measures of Speech Intelligibility.

When a new commercial vehicle project begins or some changes are necessary in the current products, the development of clutch pedals has a strong dependence with the powertrain characteristics which generally affects the clutch behavior and its actuation system. Although theoretical analyses are always taken into consideration, experimental procedures in bench tests and vehicles play an important role in the determination of new configurations for the clutch actuation system. Nowadays cost reduction, unification and quality gains must be considered in the project and development process. The above considerations mean that the work in bench tests regarding clutch actuation systems must be emphasized to simulate their behavior in the vehicle.

The objective of this paper is to present the update procedures and the future tendencies for the diagnosis projects in commercial vehicles, specially buses and trucks. The constant increase in the number of components and electronic systems in commercial vehicles demands that the subject “Diagnosis” be treated and previously defined, while the vehicle is in the project phase. The final goal of this thought is to provide to the vehicle the best possible acting of all the electronics systems placed in vehicle, and, as a consequence, the best running of the On-Board and Off-Board diagnosis systems which should assist the customer needs directly. The tendency is to project the vehicles of the same brand in the same conceptual line facilitating the assembly work in production line and the after sales support.

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.

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.