On the Virtualization of Audio Transducers

In audio transduction applications, virtualization can be defined as the task of digitally altering the acoustic behavior of an audio sensor or actuator with the aim of mimicking that of a target transducer. Recently, a digital signal preprocessing method for the virtualization of loudspeakers based on inverse equivalent circuit modeling has been proposed. The method applies Leuciuc’s inversion theorem to obtain the inverse circuital model of the physical actuator, which is then exploited to impose a target behavior through the so called Direct–Inverse–Direct Chain. The inverse model is designed by properly augmenting the direct model with a theoretical two-port circuit element called nullor. Drawing on this promising results, in this manuscript, we aim at describing the virtualization task in a broader sense, including both actuator and sensor virtualizations. We provide ready-to-use schemes and block diagrams which apply to all the possible combinations of input and output variables. We then analyze and formalize different versions of the Direct–Inverse–Direct Chain describing how the method changes when applied to sensors and actuators. Finally, we provide examples of applications considering the virtualization of a capacitive microphone and a nonlinear compression driver

Efficient Continuous Beam Steering for Planar Arrays of Differential Microphones

Performing continuous beam steering, from planar arrays of high-order differential microphones, is not trivial. The main problem is that shape-preserving beams can be steered only in a finite set of privileged directions, which depend on the position and the number of physical microphones. In this letter, we propose a simple and computationally inexpensive method for alleviating this problem using planar microphone arrays. Given two identical reference beams pointing in two different directions, we show how to build a beam of nearly constant shape, which can be continuously steered between such two directions. The proposed method, unlike the diffused steering approaches based on linear combinations of eigenbeams (spherical harmonics), is applicable to planar arrays also if we deal with beams characterized by high-order polar patterns. Using the coefficients of the Fourier series of the polar patterns, we also show how to find a tradeoff between shape invariance of the steered beam, and maximum angular displacement between the two reference beams. We show the effectiveness of the proposed method through the analysis of models based on first-, second-, and third-order differential microphones

HandMonizer: a case study for personalized digital musical instrument design

The rapid evolution in technology has found its way to introducing novelty in today’s live music performances. In this context, the development of Digital Musical Instruments (DMIs) has obtained increasing attention in recent years. In this paper, we present the development of a DMI called Handmonizer, an interactive artist-oriented harmonizer for musical performance adapted to the needs of a specific singer. A key component of our work is the combination of hand motion recognition and audio signal processing to obtain a smoother interaction. We describe the development methodology, but we also focus on our collaboration with the artist to conceptualize and then refine this tool until the development of the final product. At the end of this paper, we define an evaluation strategy, collecting feedback with a questionnaire addressed to the singer. Our aim in presenting this evaluation strategy is to help other engineers keen to develop cutting-edge technologies by working in partnership with artists. While results are not definitive, we believe that the chosen methodology could be of interest to other DMI researchers. Moreover, the modular nature of the Handmonizer makes it easily adaptable to further developments concerning the Internet of Sounds (IoS) and Networked Music Performances (NMP)

The effect of humidity on the CO2/N2 separation performance of copolymers based on hard polyimide segments and soft polyether chains: Experimental and modeling

In this work, we studied two copolymers formed by segments of a rubbery polyether (PPO or PEO) and of a glassy polyimide (BPDA-ODA or BKDA-ODA) suitable for gas separation and CO2 capture. Firstly, we assessed the absorption of water vapor in the materials, as a function of relative humidity (R.H.), finding that the humidity uptake of the copolymers lies between that of the corresponding pure homopolymers values. Furthermore, we studied the effect of humidity on CO2 and N2 permeability, as well as on CO2/N2 selectivity, up to R.H. of 75%. The permeability decreases with increasing humidity, while the ideal selectivity remains approximately constant in the entire range of water activity investigated. The humidity-induced decrease of permeability in the copolymers is much smaller than the one observed in polyimides such as Matrimid® confirming the positive effect of the polyether phase on the membrane performance.Finally, we modeled the humidity-induced decrease of gas solubility, diffusivity and, consequently, permeability, using a suitable approach that considers the free volume theory for diffusion and LF model for solubility. Such model allows estimating the extent of competition that the gases undergo with water during sorption in the membranes, as a function of the relative humidity, as well as the expected reduction of free volume by means of water molecules occupation and consequent reduction of diffusivity. Keywords: CO2 capture, Humid gas permeation, Transport properties in polymeric membranes, Water vapor sorption, Modelin

Generalized Wave Digital Filter Realizations of Arbitrary Reciprocal Connection Networks

In this paper, an existing approach for modeling and efficiently implementing arbitrary reciprocal connection networks using wave digital (WD) scattering junctions based on voltage waves is extended to be used in a broader class of WD filters (WDFs) based on different kinds of waves. A generalized wave definition which includes traditional voltage waves, current waves, and power-normalized waves as particular cases is employed. Closed-form formulas for computing the scattering matrices of the junctions are provided. Moreover, the approach is also extended to the family of Biparametric WDFs, which have been recently introduced in the literature

Wave digital modeling of the diode-based ring modulator

The ring modulator is a strongly nonlinear circuit common in audio gear, especially as part of electronic musical instruments. In this paper, an accurate model based on Wave Digital (WD) principles is developed for implementing the ring modulator as a digital audio effect. The reference circuit is constituted of four diodes and two multi-winding transformers. The proposed WD implementation is based on the Scattering Iterative Method (SIM), recently developed for the static analysis of large nonlinear photovoltaic arrays. In this paper, SIM is shown to be suitable for implementing also audio circuits for Virtual Analog applications, such as the ring modulator, since it is stable, robust and comparable to or more efficient than state-of-the-art strategies in terms of computational cost

Genetic diversity of Cornigliese sheep breed using STR markers

To preserve sheep biodiversity is an important issue as the most productive breeds are becoming dependent on intensive management and breeders are abandoning the traditional breeds. The Cornigliese sheep is a local breed from Parma Apennine. In the last centuries it was crossed with Merino and Bergamasca breeds. The aim of this work is to investigate the genetic variability in the Cornigliese breed using 27 microsatellite markers. A total of 144 individual blood samples were randomly collected from the following breeds: Cornigliese, Bergamasca, Appenninica and Spanish Merino. The Palmera breed was used as out-group. A total of 344 alleles were detected. The average expected heterozygosity ranged from a maximum of 0.77 in Appenninica to a minimum of 0.68 in Bergamasca. In general,Cornigliese showed heterozygosity estimates less than expected. The Reynolds weighted genetic distance among the breeds highlighted a clear cluster, including Cornigliese and Bergamasca. As expected, they appeared in close neighbourhood in the tree because of the historic crossbreeding practices between these two breeds. Results of STRUCTURE analyses show that the four studied breeds were discriminated into separate clusters, even if Cornigliese has some individual related to Bergamasca and Spanish Merino. This work confirmed the historical information about the origin of Cornigliese breed which reports gene flow among these breeds. The genetic parameters show a moderate value of inbreeding in Cornigliese and therefore this breed should be monitored due the low number of individuals that compose it

Modificación de un equipo de medición de absorción e impedancia acústica para adaptarlo a la norma ASTM C-384

La Sección Acústica y Vibraciones del LEMIT cuenta con un equipo marca Brüel & Kjaer, modelo 4002, que permite la rápida y fácil determinación de los coeficientes de absorción acústica. Al tratar de medir materiales con bajos coeficientes de absorción, aparecen ciertas incertidumbres en la lectura de los valores obtenidos, que ponen en evidencia la imposibilidad de obtener resultados confiables. Un análisis de este funcionamiento deficiente demostró que se producían excesivas vibraciones en el instrumento, introduciéndole una absorción a la del material a medir, lo cual mostró la convéniencia de rediseñar el equipo para adecuarlo a la medida de bajos coeficientes de absorción.The Acoustics and Vibration Laboratory of LEMIT has a Briiel & Kjaer instrument, model 4002, that allows the fast and easy determination of acoustic absorption coefficients. Trying to measuring materials with low coefficients there is some uncertainty in the obtaind values, that shows the impossibility of reliable results. An analysis of this deficiency shows that the instrument vibrates excessively introducing an additional absorption, pointing out the convenience of redesign the equipment to measure low absorption coefficients