Modeling Frequency-Dependent Boundaries as Digital Impedance Filters in FDTD and K-DWM Room Acoustics Simulations

A new method for modeling-frequency-dependent boundaries in finite-difference time-domain (FDTD) and Kirchhoff variable digital waveguide mesh (K-DWM) room acoustics simulations is presented. The proposed approach allows the direct incorporation of a digital impedance filter (DIF) in the Multidimensional (2D or 3D) FDTD boundary model of a locally reacting surface. An explicit boundary update equation is obtained by carefully constructing a Suitable recursive formulation. The method is analyzed in terms of pressure wave reflectance for different wall impedance filters and angles of incidence. Results obtained from numerical experiments confirm the high accuracy of the proposed digital impedance filter boundary model, the reflectance of which matches locally reacting surface (LRS) theory closely. Furthermore a numerical boundary analysis (NBA) formula is provided as a technique for an analytic evaluation of the numerical reflectance of the proposed digital impedance filter boundary formulation.

Parametric FIR Design of Propagation Loss Filters in Digital Waveguide String Models

One of the attractive features of sound synthesis by physical modeling is the potential to build acoustic-sounding digital instruments that offer more flexibility and different options in its design and control than their real-life counterparts. In order to develop such virtual-acoustic instruments, the models they are based on need to be fully parametric, i.e., all coefficients employed in the model are functions of physical parameters that are controlled either online or at the (offline) design stage. In this letter we show how propagation losses can be parametrically incorporated in digital waveguide string models with the use of zero-phase FIR filters. Starting from the simplest possible design in the form of a three-tap FIR filter, a higher-order FIR strategy is presented and discussed within the perspective of string sound synthesis with digital waveguide models.

Effectiveness of different footbath solutions in the treatment of digital dermatitis in dairy cows

Three experiments were conducted to test the effectiveness of different footbath solutions and regimens in the treatment of digital dermatitis (DD) in dairy cows. During the study, groups of cows walked through allocated footbath solutions after milking on 4 consecutive occasions. All cows were scored weekly for DD lesion stage on the hind feet during milking. A “transition grade” was assigned on the basis of whether the DD lesions improved (1) or deteriorated or did not improve (0) from week to week. This grade per cow was averaged for all cows in the group. In experiment 1, 118 cows were allocated to 1 of 3 footbath treatments for 5 wk: (1) 5% CuSO4 each week, (2) 2% ClO- each week, or (3) no footbath (control). The mean transition grade, and proportion of cows without DD lesions at the end of the trial were significantly higher for treatment 1 above (0.36, 0.13, and 0.11, respectively; standard error of the difference, SED=0.057). In experiment 2, 117 cows were allocated to 1 of 4 footbath treatment regimens for 8 wk: (1) 5% CuSO4 each week, (2) 2% CuSO4 each week, (3) 5% CuSO4 each fortnight, or (4) 2% CuSO4 each fortnight. For welfare reasons, cows allocated to the weekly and fortnightly footbath regimens had an average prevalence of >60% and =25% active DD at the start of the trial, respectively. Significantly more cows had no DD lesions (0.53 vs. 0.36, respectively; SED=0.049), and the mean transition grade of DD lesions was higher in the 5% compared with the 2% weekly CuSO4 treatment (0.52 vs. 0.38, respectively; SED=0.066). Similarly, significantly more cows had no DD lesions in the 5% compared with the 2% fortnightly CuSO4 treatments (0.64 vs. 0.47, respectively; SED=0.049). In experiment 3, 95 cows were allocated to 1 of 3 footbath treatments: (1) each week alternating 5% CuSO4 with 10% salt water, (2) each week alternating 5% CuSO4 with water, or (3) 5% CuSO4 each fortnight (control). After 10 wk, more cows had no DD in the salt water treatment than in the control treatment (0.35 vs. 0.26, respectively; SED=0.038), but levels of active lesions were higher for this treatment than in the other 2 treatments (0.17, 0.00, and 0.13, respectively; SED=0.029). Treatment did not affect mean transition grade of DD lesions. In conclusion, CuSO4 was the only footbath solution that was consistently effective for treatment of DD. In cases when DD prevalence was high, a footbath each week using 5% CuSO4 was the most effective treatment.

Digital Musical Interactions: Performer-System Relationships and their Perception by Spectators

This article adopts an ecological view of digital musical interactions, first considering the relationship between performers and digital systems, and then spectators’ perception of these interactions. We provide evidence that the relationships between performers and digital music systems are not necessarily instrumental in the same was as they are with acoustic systems, and nor should they always strive to be. Furthermore, we report results of a study suggesting that spectators may not perceive such interactions in the same way as performances with musical instruments. We present implications for the design of digital musical interactions, suggesting that designers should embrace the reality that digital systems are malleable and dynamic, and may engage performers and spectators in different modalities, sometimes simultaneously.

A Framework for the Evaluation of Digital Musical Instruments

At the outset of a discussion of evaluating digital musical instruments, that is to say instruments whose sound generators are digital and separable though not necessarily separate from their control interfaces (Malloch, 2006), it is reasonable to ask what the term evaluation in this context really means. After all, there may be many perspectives from which to view the effectiveness or otherwise of the instruments we build. For most performers, performance on an instrument becomes a means of evaluating how well it functions in the context of live music making, and their measure of success is the response of the audience to their performance. Audiences evaluate performances on the basis of how engaged they feel they have been by what they have seen and heard. When questioned, they are likely to describe good performances as “exciting,” “skillful,” “musical.” Bad performances are “boring,” and those which are marred by technical malfunction are often dismissed out of hand. If performance is considered to be a valid means of evaluating a musical instrument, then it follows that, for the field of DMI design, a much broader definition of the term “evaluation” than that typically used in human-computer interaction (HCI) is required to reflect the fact that there are a number of stakeholders involved in the design and evaluation of DMIs. In addition to players and audiences, there are also composers, instrument builders, component manufacturers, and perhaps even customers, each of whom will have a different concept of what is meant by “evaluation.”

Low power field programmable gate array implementation of fast digital signal processing algorithms: characterisation and manipulation of data locality

Dynamic power consumption is very dependent on interconnect, so clever mapping of digital signal processing algorithms to parallelised realisations with data locality is vital. This is a particular problem for fast algorithm implementations where typically, designers will have sacrificed circuit structure for efficiency in software implementation. This study outlines an approach for reducing the dynamic power consumption of a class of fast algorithms by minimising the index space separation; this allows the generation of field programmable gate array (FPGA) implementations with reduced power consumption. It is shown how a 50% reduction in relative index space separation results in a measured power gain of 36 and 37% over a Cooley-Tukey Fast Fourier Transform (FFT)-based solution for both actual power measurements for a Xilinx Virtex-II FPGA implementation and circuit measurements for a Xilinx Virtex-5 implementation. The authors show the generality of the approach by applying it to a number of other fast algorithms namely the discrete cosine, the discrete Hartley and the Walsh-Hadamard transforms.