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The Hybrid FE-SEA method is a recently developed numerical technique that deals with the so-called mid-frequency problem. Such problems involve the dynamic analysis of systems that include, at the same frequency range, components with high and low modal density. Systems with a reduced number of modes are usually modeled using deterministic methods, as the Finite Element (FE) Method, while modal dense systems need to be treated by means of statistical methods such as the Statistical Energy Analysis (SEA). Neither FE nor SEA can properly describe a system that displays the mid-frequency behavior due to a prohibitive computational cost (FE) or the lack of accuracy (SEA). The floor structure of an aircraft is a typical case of a mid frequency problem, where the floor beams are relatively rigid and have very few modes while the floor panels have a very high modal density.

The great challenge in designing is to be able to foresee vibration and acoustic behavior of the system or component before the first real prototype. A better prediction of this behavior should prevent system operation of future troubleshooting. This work presents a numerical analysis based on Acoustic Transfer Vector (ATV) and Modal Acoustic Transfer Vector (MATV) techniques to predict radiating noise of a vibrating structure. The FEM model can also be brought as close as possible to the reality by using experimental test data - loading, modal parameters - allowing applying also correlation and updating techniques. This hybrid methodology is a possibility to do a better prediction of the under design component's or system's behavior of components or systems under design.

Measurement of sound intensity involves determining the sound pressure and the particle velocity at the same position simultaneously. The p-p method for measuring intensity uses two pressure microphones that determine the particle velocity component in the direction of the axis of the probe by a finite-difference approximation to the pressure gradient in Euler's equation of motion, and the sound pressure is simply the average of the two pressure signals. The p-u method uses a sound intensity probe that combines an acoustic particle velocity transducer with a pressure microphone (p-u probe). These two sound intensity methods could be used to measure the sound power level of sources.

One of the important environmental parameters in engine emissions and air-to-fuel ratio is the Barometric pressure. In order to determine the full impact of this environmental variable in Tecumseh engines an experiment was conducted. The experiment was conducted along five distinct points of barometric pressure from 1000 m to sea level. In these five environmental conditions CO and CO2 levels were measured. Also, as the most important parameter, and main object of the study, air-to-fuel ratio - λ, was determined. The purpose of this paper is to determine a reference engine running condition to reproduce it in Laboratory, as close as possible, to the real sea level operation. Finally an oxygenated fuel is presented as ally to compensate the lack of oxygen at high altitudes.

TMT-Motoco do Brasil is an enterprise from Tecumseh Group. TMT develops lawnmowers, lawn trimmers and walk behind mowers engines. The present work has a purpose to present a methodology for vibration measuring in such particular engines. There is no work in Brazilian literature related to such kind of engines and that is the main reason for this paper. The actual methodology presents a detailed procedure to evaluate engine vibration, trough spectra measurements, order analysis and signature analysis and how to design an experiment to evaluate engine vibration. Through order analysis, engines were tested in current applications (walk behind mowers) and test stands to obtain frequency responses. Such experiments are the initial part of a larger analysis of vibroacoustic behavior of mowers engines.