The problem of offset in acoustic pulse reflectometry

Acoustic pulse reflectometry has become established as a useful non-invasive technique for measuring a variety of duct properties. A sound pulse is injected into the duct under investigation and the resultant reflections are recorded. Suitable analysis of the reflections yields the input impulse response of the duct, from which both its input impedance and its internal dimensions can be calculated. However, an input impulse response measurement made using acoustic pulse reflectometry generally contains an offset. Unless this offset is removed, the application of a bore reconstruction algorithm results in a calculated duct profile which expands or contracts spuriously. In this paper, the offset in an input impulse response measurement is shown to consist of both constant and time-varying components. Methods of preventing or removing these DC and time-varying offsets are proposed and subsequent improvements to the bore reconstruction accuracy are demonstrated

Developing and evaluating a hybrid wind instrument

A hybrid wind instrument generates self-sustained sounds via a real-time interaction between a computed excitation model (such as the physical model of human lips interacting with a mouthpiece) and a real acoustic resonator. Attempts to produce a hybrid instrument have so far fallen short, in terms of both the accuracy and the variation in the sound produced. The principal reason for the failings of previous hybrid instruments is the actuator which, controlled by the excitation model, introduces a fluctuating component into the air flow injected into the resonator. In the present paper, the possibility of using a loudspeaker to supply the calculated excitation signal is evaluated. A theoretical study has facilitated the modeling of the loudspeaker-resonator system and the design of a feedback and feedforward filter to successfully compensate for the presence of the loudspeaker. The resulting self-sustained sounds are evaluated by a mapping of their sound descriptors to the input parameters of the physical model of the embouchure, both for sustained and attack sounds. Results are compared with simulations. The largely coherent functioning confirms the usefulness of the device in both musical and research contexts

Virtual Pitch and Pitch Shifts in Church Bells

It is well established that musical sounds comprising multiple partials with frequencies approximately in the ratio of small integers give rise to a strong sensation of pitch even if the lowest or fundamental partial is missing—the so-called virtual pitch effect. Experiments on thirty test subjects demonstrate that this virtual pitch is shifted significantly by changes in the spacing of the constituent partials. The experiments measured pitch by comparison of sounds of similar timbre and were automated so that they could be performed remotely across the Internet. Analysis of the test sounds used shows that the pitch shifts are not predicted by Terhardt’s classic model of virtual pitch. The test sounds used were modelled on the sounds of church bells, but a further experiment on seventeen test subjects showed that changes in partial amplitude only had a minor effect on the pitch shifts observed, and that a pitch shift was still observed when two of the lowest frequency partials were removed, so that the effects reported are of general interest

Properties of "35" Spin-(5/2) Baryon Resonances in a Model with Broken SU(3)

We investigate the properties of a set of J =(5/2)^+ resonances appearing in a 35-dimensional representation of SU(3), as proposed by Abers, Balázs, and Hara. A simple dynamical calculation gives an estimate for the mass differences within the supermultiplet. The matrix elements for the SU(3) allowed decays into meson plus resonance are given in terms of one parameter and the SU(3)-violating matrix elements for decay into meson plus baryon are given by two parameters

Attribution of injury in the shrimp antidumping case: A simultaneous equations approach

We apply a simultaneous equations framework, similar to that of Prusa and Sharp (2001), to the recent shrimp antidumping investigation in order to determine how much injury to the domestic industry—proxied by deterioration in domestic shrimp prices—is attributable to subject imports versus other market factors. We construct an econometric model then estimated with three-stage least squares (3SLS). We then apply the movements of each explanatory variable over the period of investigation (POI) to its respective coefficient in order to determine how much injury is attributable to that particular market factor. We find that subject and non-subject imports were essentially equal causes of injury to the domestic industry.3SLS

Spectral pitch distance and microtonal melodies

We present an experiment designed to test the effectiveness of spectral pitch distance at modeling the degree of “affinity” or “fit” of pairs of successively played tones or chords (spectral pitch distance is the cosine distance between salience-weighted, Gaussian-smoothed, pitch domain embeddings of spectral pitches—typically the first eight to ten partials of a tone). The results of a previously conducted experiment, which collected ratings of the perceived similarity and fit of root-position major and minor triads, suggest the model works well for pairs of triads in standard 12-tone equal temperament tunings. The new experiment has been designed to test the effectiveness of spectral pitch distance at modeling the affinity of tones in microtonal melodies where the partials of the tones can be variably tempered between being perfectly harmonic and perfectly matched to the underlying microtonal tuning. The use of microtonal tunings helps to disambiguate innate perceptual (psychoacoustical) responses from learned (cultural) responses. Participants are presented with a software synthesizer containing two unlabeled controls: one adjusts the precise tuning of the tones; the other adjusts the extent to which the spectrum is tempered to match the tuning (as set by the first control). A selection of microtonal melodies are played in different tunings, and the participants adjust one, or both, controls until they find a “sweet spot” at which the music sounds most “in-tune” and the notes best “fit” together. The results of these experiments will be presented and discussed

Metrics for pitch collections

Models of the perceived distance between pairs of pitch collections are a core component of broader models of the perception of tonality as a whole. Numerous different distance measures have been proposed, including voice-leading, psychoacoustic, and pitch and interval class distances; but, so far, there has been no attempt to bind these different measures into a single mathematical framework, nor to incorporate the uncertain or probabilistic nature of pitch perception (whereby tones with similar frequencies may, or may not, be heard as having the same pitch). To achieve these aims, we embed pitch collections in novel multi-way expectation arrays, and show how metrics between such arrays can model the perceived dissimilarity of the pitch collections they embed. By modeling the uncertainties of human pitch perception, expectation arrays indicate the expected number of tones, ordered pairs of tones, ordered triples of tones and so forth, that are heard as having any given pitch, dyad of pitches, triad of pitches, and so forth. The pitches can be either absolute or relative (in which case the arrays are invariant with respect to transposition). We provide a number of examples that show how the metrics accord well with musical intuition, and suggest some ways in which this work may be developed

Formal structure of scientific journals and types of scientific papers

Les revistes científiques tenen una estructura formal que cal que els qui hi estan en contacte (autors, lectors i editors) comprenguin per tal que els siguin útils. L'autor analitza els tipus d'article que hi ha a tres revistes mèdiques i a una altra d'informació científica general (comunicacions preliminars, articles de revisió, editorials, secció de correspondència) i com s'estructuren els articles de recerca, perquè les altres seccions són de format més lliure.Scientific journals have a formal structure that has to be understood by all those who read it (authors, readers and editors) in order to be useful. The author analyses different types of articles in three medical journals and one of general science (preliminar communications, review articles, editorials, letters to the editor) and how research articles are structurated, because the other sections have a more free format

Training Big Random Forests with Little Resources

Without access to large compute clusters, building random forests on large datasets is still a challenging problem. This is, in particular, the case if fully-grown trees are desired. We propose a simple yet effective framework that allows to efficiently construct ensembles of huge trees for hundreds of millions or even billions of training instances using a cheap desktop computer with commodity hardware. The basic idea is to consider a multi-level construction scheme, which builds top trees for small random subsets of the available data and which subsequently distributes all training instances to the top trees' leaves for further processing. While being conceptually simple, the overall efficiency crucially depends on the particular implementation of the different phases. The practical merits of our approach are demonstrated using dense datasets with hundreds of millions of training instances.Comment: 9 pages, 9 Figure

The community waste sector and waste services in the UK: current state and future prospects

YesTheory predicts that the voluntary or community sector will contribute a range of services that are not delivered by the state or private sectors. This paper examines the changing contributions of the community waste sector in the UK to reflect upon these claims. A rosy picture of the community waste sector is presented from research on the sector in 2002, with a growing number of organisations carrying out a range of services, drawing on multiple and diverse sources of funding. More recent evidence, and information drawn from outside the sector, however, suggests that regulation, competition, and changes to funding regimes are putting the sector under considerable pressure, such that it is likely to change, and that some parts of it will contract. In terms of the claims from theory, the paper finds evidence that the community sector can and has been innovative in the services it provides and the way that it provides them, though similar innovations may emerge from the private and public sectors. The sparse evidence on participation and recycling rates in kerbside and civic amenity sites are equivocal on whether the sector provides enhanced communication as theory would predict. Overall, the paper highlights the difficulty in achieving direct comparisons between the waste sectors without specific focused research for this purpose. It concludes that the challenge for European, national and local government is to influence the necessarily constructed waste markets in a way which will enhance rather than discourage service providers to innovate in the waste material collected, and to communicate effectively with the public whom they serve. Such policies promise to encourage the effective delivery of sustainable waste services from all three - public, private and community - sectors