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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.

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).

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.

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 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.

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.

This article has as objective the demonstration of a methodology to create component test rigs using numerical simulation techniques (FEM - Finite Element Modelling) as an aiding tool. It also emphasises the interaction between modern design procedures and experimental testing, regarding their consequences to product development. The case study was the development of a prototype chassis components durability test rig. The target was to reproduce a failure occurring at a crossbeam subframe on the assembly with the leaf spring mounting in order to test possible proposed solutions. An initial rig concept was created using experimental data. This conception failed to reproduce the crack at the point where it occurred in the prototype. A new rig was virtually designed and simulated. As the simulation showed proper results, it encouraged the construction of this new rig, which reproduced the failure as expected.

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.

Due to the growing need to reduce the development time of new products, a tendency to rationalize field tests through test benches, in shorter times and with lower costs, has been noted in recent years. During the 90's, such a tendency has generated, in the automotive industry, a great effort to substitute classic field tests, which until recently represented 70% of the development work, for bench tests, with benches well “calibrated” in relation to the traditional methodology. The present work intends to show the development of a test bench to simulate solar radiation and relative humidity effects upon parts and interior lining materials of truck cabins. The traditional test was carried out exposing the cabin to weather conditions in predetermined locations, or in a hot-house, monitoring the cabin interior for temperature and relative humidity variations.

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.

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.

A mathematical simulation model was developed to calculate the cooling loads in a cab. The cooling loads calculations are described: Solar irradiation through glasses, conduction through the body walls and glasses, conduction through motor compartment, fresh air intake/infiltrations, people and equipments. Fields experiments were conducted to evaluate the conduction through walls and glasses and the total cooling load models. Precision less than 5% was gotten between experimental measurements and model results. In the summer situation, studies about the effects of the cab orientation, the time, the external paint and the tint of the glasses in changing the conduction and solar radiation cooling loads, were conducted. Cab orientation and the time can change this cooling loads by 225%. Variation by 30% was gotten from different paints and glasses.

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.

The paper goes beyond the conventional way of looking at Loudness. We go into the calculation procedures taking into consideration two methods coming from the work of two researchers: Zwicker and Stevens. These methods are described in ISO 532. Instead of going to the traditional way of comparing the overall noises we penetrate in the calculation processes, step by step, getting subsidies to analyze the contributions of each frequency band. We applied the two methods using some random sound pressure spectra we generated. We are able to compare the total Loudnesses in both methods using a least-square fit with linear approximation. The spectra of contributions in sones in third-octave bands are also compared for both methods, through the development of simple mathematical expressions which are able to identify the parcel correspondent to each third-octave band.

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.