Model-oriented review and multi-body simulation of the ossicular chain of the human middle ear

The ossicular chain of the human middle ear has a key role in sound conduction since it transfers vibrations from the tympanic membrane to the cochlea, connecting the outer and the inner part of the hearing organ. This study reports firstly a description of the main anatomical features of the middle ear to introduce a detailed survey of its biomechanics, focused on model development, with a collection of geometric, inertial and mechanical/material parameters. The joint issues are particularly discussed from the perspective of developing a model of the middle ear both explanatory and predictive. Such a survey underlines the remarkable dispersion of data, due also to the lack of a standardization of the experimental techniques and conditions. Subsequently, a 3D multi-body model of the ossicular chain and other structures of the middle ear is described. Such an approach is justified as the ossicles were proven to behave as rigid bodies in the human hearing range and was preferred to the more widely used finite element one as it simplifies the model development and improves joint modeling. The displacement of the umbo (a reference point of the tympanic membrane) in the 0.3-6. kHz frequency range was defined as input of the model, while the stapes footplate displacement as output. A parameter identification procedure was used to find parameter values for reproducing experimental and numerical reference curves taken from the literature. This simple model might represent a valid alternative to more complex models and might provide a useful tool to simulate pathological/post-surgical/post-traumatic conditions and evaluate ossicular replacement prostheses. © 2012 IPEM

A psychoacoustic approach for sound quality assessment of automotive power windows

Psychoacoustic methodologies were investigated and applied to a case study within a cooperation project of the University of Pisa and Magna Closures S.p.A. mainly focused on the acoustics of power windows. The project included tests on closing-opening event sequences of the power window rail, to evaluate the component noise. Different trials were performed varying the test conditions. Time-frequency analyses, psychoacoustic metrics and models were applied to the Sound Pressure Level (SPL) time functions of the raw microphone signals and compared with threshold values from the literature. Scalar parameters quantifying the electric motor steadiness were also computed to characterize the noise excitation source while accelerometer signals were analysed in the frequency domain to extract modal parameters. The SPL time function appeared highly related to supply voltage, motor type and silent block insertion whereas psychoacoustic parameters were able to highlight further peculiarities of sound timbre

Studio di fattibilità di un orecchio virtuale

La ricerca intrapresa dagli autori ha come obiettivo la realizzazione di un “orecchio virtuale”, ovvero di un modello “completo” psico-acustico della percezione uditiva umana, che tenga conto di contributi alternativi alla via aerea normale quali contributi derivanti da vie tissutali (in particolare ossee) e fluide e contributi a frequenze ultrasoniche ed infrasoniche. Dato che risulta necessario studiare tecniche specifiche di modellazione e simulazione per ciascuna parte anatomica, nel presente lavoro sono stati approfonditi ed applicati a geometrie semplificate bidimensionali e tridimensionali dell’orecchio esterno, alcuni metodi (principalmente metodo ad elementi finiti spettrali (SFE), metodo ad elementi finiti generalizzato (GFEM)) di generalizzazione ed estensione del metodo agli elementi finiti classico (FEM) (principalmente metodo ad elementi finiti spettrali (SFE), metodo ad elementi finiti generalizzato (GFEM)). Tali metodi permettono di ottenere un’elevata accuratezza dei risultati delle simulazioni di trasmissione acustica con numero inferiore di nodi della meshdiscretizzazione rispetto alla regola convenzionalmente accettata per il FEM di dieci punti per lunghezza d’ondaun costo computazionale inferiore rispetto ai metodi tradizionali

An image formation model for Secondary Ion Mass Spectrometry imaging of biological tissue samples RID A-6953-2008

Secondary Ion Mass Spectrometry (SIMS) can provide distribution images of elements and molecular fragments with high sensitivity and spatial resolution. This study aims to exploit the potential of this modality as an imaging technique for biomedical applications. A model of image generation was developed and validated on experimental SIMS images. The model allowed for the selection of standard distance deviation (SDD) and nearest neighbor index (NNI) as suitable indices for the characterization of SIMS images, as they have been associated with sample morphology. Two regression models were proposed to correlate the SDD index and NNI with an index of effectiveness and acquisition parameters. The SDD index, due to its linear relationship with the image noise parameter, was less sensitive to noise. The model was then applied to study the effect of instrumental and analytical parameters, such as pre-sputtering time, on image generation. (C) 2010 Elsevier B. V. All rights reserved