Acoustic characterization of the compressor stage of an automotive turbocharger

Turbochargers are a key component of internal combustion engines in the automotive industry. They contribute to the downsizing trend and allow constructors to respect more and more severe emissions norms. However, the turbocharger behaves as an acoustic source in the air intake system, and has an influence in the acoustic waves travelling in it. The passive and active acoustic characteristics of the turbocharger can be used as a starting point for the design and development of acoustic devices in the air intake system, or as an input of acoustic 1D simulations of engine intake lines. In this paper both the active and passive acoustic behaviours of a compressor stage of two different automotive turbochargers were studied. The active acoustic effect of the compressor was studied by its characterization as an acoustic source. This is performed experimentally by the computation of the acoustic power at the inlet and outlet of the compressor. This power was obtained by performing plane wave decomposition with the beamforming method over all the working points of the compressor map. Using the pressure decomposition, the acoustic intensity is calculated and then the acoustic power. In this way the acoustic power delivered by the compressor on the air intake system is measured. The passive acoustic effect is studied by the measurement of the acoustic Transmission Loss (TL) of the compressor through the calculation of its scattering matrix under two port considerations. Using also the beamforming method to decompose the incident and reflected waves at the inlet and outlet of the compressor, the transmission coefficients in both upwards and downwards directions are computed. Experimentally the TL of a static turbocharger was measured and results were extrapolated by a model to obtain the TL of the compressor over different working points of the compressor map. Numerically, 3D acoustic simulations were performed in order to compare to the model results. Numerical and experimental results were compared, and a predictive model for TL is proposed. This model will be compared in the future to real TL measurements on a working turbocharger

FPGA-based architectures for acoustic beamforming with microphone arrays : trends, challenges and research opportunities

Over the past decades, many systems composed of arrays of microphones have been developed to satisfy the quality demanded by acoustic applications. Such microphone arrays are sound acquisition systems composed of multiple microphones used to sample the sound field with spatial diversity. The relatively recent adoption of Field-Programmable Gate Arrays (FPGAs) to manage the audio data samples and to perform the signal processing operations such as filtering or beamforming has lead to customizable architectures able to satisfy the most demanding computational, power or performance acoustic applications. The presented work provides an overview of the current FPGA-based architectures and how FPGAs are exploited for different acoustic applications. Current trends on the use of this technology, pending challenges and open research opportunities on the use of FPGAs for acoustic applications using microphone arrays are presented and discussed

Localización de fuentes cerebrales para la caracterización de la demencia debida a la enfermedad de Alzheimer

En el presente Trabajo de Fin de Máster se localizaron tanto espacial como espectralmente las alteraciones de los generadores neuronales provocadas por el deterioro cognitivo leve y la demencia debidos a la enfermedad de Alzheimer. Para ello, se midió la potencia relativa a nivel de sensor y nivel de fuente, y se evaluó el grado de relación de dichas medidas. Los resultados muestran que los primeros cambios aparecen en la banda zeta y conforme avanza la demencia se extienden a las bandas beta y alfa. La correlación entre la potencia relativa a nivel de sensor y a nivel de fuente es significativa, sobre todo para bandas bajas y en la zona frontal y occipital.Departamento de Teoría de la Señal y Comunicaciones e Ingeniería TelemáticaMáster en Ingeniería de Telecomunicació