Echo Effect Research Articles

Layered voice musical self-accompaniment system

The practice of this invention enables a musician to augment a main "lead voice" performance by extemporaneously deriving from particularly selected notes of the main performance a separate synthesized accompaniment in which particularly selected notes may be controllably time-extended (e.g. sustained) singly or in a group, in effect "detached" from the lead voice. The first of a pair of low profile footswitches enables/cancels accompaniment triggering; the second enables/cancels accompaniment time-extension. Switch logic is implemented such that the first switch can never override the second switch to cancel time-extension; thus a musician operating the switches interactively, typically one with each foot, is enabled, through strategic timing relative to the lead notes, to trigger accompaniment notes from particularly selected lead notes, to controllably time-extend particularly selected accompaniment notes, and to accumulate groups of such time-extended accompaniment notes. The invention is applicable to a wide range of lead voice sources including the guitar, The Chapman Stick® fingerboard instrument and its synthesizer controller version. The Grid®, guitar synthesizers, keyboard synthesizers, as well as acoustic, electrical and synthesized musical instruments of various types and even the human voice. The invention may be implemented using available MIDI-based equipment, specially configured. The practices are applicable to sustain, delay and echo effects. As a refinement, pitch bending in the accompaniment may be separately disabled, thus emphasizing pitch bending performed in the lead voice.

Frequency dependent conductance and dielectric permittivity

Starting from the basic equation for the pair distribution function in nonequilibrium which takes into account the echo effect, the theory of electrolytes in low frequency fields is investigated. For explicit calculations of the pair distribution functions, the strong coupling approximation (SCA) for distances smaller than the Bjerrum distance is used. The result is discussed as the effect of ionic motion on the complex permittivity of the solution. In the limiting case of large values of the Bjerrum parameier it identifies with the effect of rotating ion pairs and allows an evaluation of the increase on the static permittivity of the electrolyte solutions.

Femtosecond photon echoes via non-Markovian dephasing

The photon echo effect in dye molecules in solution has not been studied since effective mechanisms for inhomogeneous line broadening are not expected. We show that photon echoes may occur on a femtosecond time scale when the observation times are shorter than the memory time of the heat bath, and hence non-Markovian features of the molecular dephasing may become relevant. The properties and the dependence of the echo on the characteristics of the non-Markovian dephasing process are studied.

Effect of tactile echo and tactile reverberation on the speech fluency of stutterers

Effect of tactile echo and tactile reverberation on the speech fluency of stutterers

Left heart opacification with peripheral venous injection of a new saccharide echo contrast agent in dogs

Opacification of the left heart chambers after venous injection of echo contrast agents with transpulmonary capabilities has been difficult to achieve because of a lack of availability of a biodegradable nontoxic agent that produces uniformly small microbubbles. SHU-508 is a new saccharide echo contrast agent that produces bubble sizes from 2 to 8 μm in diameter, capable of traversing the pulmonary capillary bed and resulting in left heart contrast. The echo intensity produced by this agent was compared with that of agitated saline solution, indocyanine green and SHU-454 (another experimental saccharide agent for right-sided contrast) during 136 injections in eight dogs. Videotaped two-dimensional echographic images were digitized and analyzed with the use of videodensitometry for peak right and left ventricular intensity, pulmonary transit times and time of persistence of contrast. The highest right ventricular intensity value (3,594 ± 1,393) was achieved with SHU-508 (p < 0.05 compared with the other agents). The right ventricular contrast seen with SHU-508 also persisted for a longer period (22.8 ± 12 s) than with the standard agents (p < 0.001).Left ventricular contrast with SHU-508 was visually evident in all 42 injections, whereas the peak left ventricular intensity was 35% as bright as that produced in the right ventricle by the same agent. Peak left ventricular intensity values from SHU-508 were compared with those from agitated saline solution injected from the pulmonary capillary wedge position in four dogs. SHU-508 produced brighter left ventricular intensity (1,281 ± 607) compared with that obtained with the saline-wedge technique (p < 0.002). The left ventricular echo contrast effect persisted for 18.8 ± 6 s compared with 8.6 ± 2 s for saline solution (p < 0.001). The pulmonary transit time for SHU-508 was 10.1 ± 5 s for the group and appeared to vary depending on individual heart rates.Thus, SHU-508 is a new saccharide echo contrast agent that produces effective opacification of the left ventricular cavity after peripheral venous injection in dogs.

Upgrading of large-scale housing estates in The Netherlands

I . Introduction After the Second World War The Netherlands experienced a persis tent housing shortage) which lasted longer than in most of the other countries of Western Europe. While housing production declined in other West European countries) The Netherlands continued in the eighties too to mainta in a housebuilding programme of I00,000 to 120,000 dwelling per year. The echo effect of the post-war birth bulge) the foreign immigrat ion and the thinning-out of families led to a development of the housing demand that again and again exceeded the forecasts . Despite the continuing shortages) in recent years a not inconsiderable vacancy has also been noted. The striking feature of this is tha t a strong concentration of vacancy occurs on cer ta in estates , whereas elsewhere within the same regional housing market excess demand manifests itself (Prak and Priemus, 1985). There is evidently a housing and district hierarchy perceived by residents in which demand is directed towards housing esta tes with a favourable price/qual i ty rat io and le t t ing problems may occur with dwellings with an unfavourable price/qual i ty rat io at the bot tom of the housing hierarchy. In this ar t ic le we describe some character is t ics of large-scale housing estates with le t t ing difficult ies (Section 2). In Section 3 we put forward the price-quali ty rat io as the central variable, tha t explains the le t tab i l i ty of housing estates . We present le t tabi l i ty isograms by means of the price/quali ty rat io of dwellings and we sketch a segmentat ion of the housing market . These exercises give us a tool for developing upgrading strategies for large-scale es ta tes (Section 4). Measures can be aimed at lowering the price (4.2.), improving the quality (4.3.) and at a be t te r adaptat ion to the changing housing market (4.4.). Therapies and prescriptions are broadly sketched for four categories of post-war estates (4.5.). After some remarks about the evaluation of measures (in Section 5) we formulate a summary and draw some conclusions (Section 6).

Directional microphone systems for teleconferencing

Many factors have contributed to historically unrealistic predictions for the growth of audio teleconferencing. Aside from the sociological issues, there exist many acoustic problems that can severely degrade the performance of present technology. A few of these problems are: the effects of reverberation, room noise, feedback, undesired speakers, and echo. At present, the most common solution for some of these problems has been to locate a microphone(s) in close proximity to the desired speaker(s) with gain switching to eliminate feedback problems. While this solution can sometimes be effective, it also introduces some compromises that are easily spotted and are considered annoying by teleconferencing users. The most notable problems are with gain switching and reverberation. These detrimental effects can be reduced by the use of highly directional microphones systems tailored to the problems of teleconferencing. The development of directional microphones and their present use in audio teleconferencing will be reviewed. Some of the highly directional microphone arrays that have been worked with will be described. Finally, comments will be given on how these new directional microphone systems address the problems of teleconferencing in small and large acoustic environments.

A subjective testing methodology for evaluating medium rate codecs for digital mobile radio applications

The planned Pan-European cellular digital mobile radio (DMR) system envisaged for the early 1990s intends to use medium rate encoding of about 16 kbit/s. At least three phases of experimentation are planned, these being: (1) national pre-selection tests. (2) European selection test, and (3) the final characterisation and verification test with associated channel coding. The first two phases intend to use listening tests only where effects due to the extra processing delay of the codecs will not be tested. An initial maximum delay target of 65 ms was set. The final phase will use conversion tests do evaluate the effects of quality, delay and echo and will be complemented by listening tests which will also be used for codec characterisation. This paper describes subjective testing methodologies adopted to select suitable candidate codecs capable of being used in the proposed DMR system. Each administration participating in the tests had to convince the European Committee (Conférence Européenne des Administrations des Postes et Télécommunications, CEPT) that their candidate codec was better than or at least as good as the speech quality of companded FM analogue 900 MHz systems currently in use in Europe.

On polarized neutron scattering from magnetized samples and the spin echo effect

The scattering of polarized neutrons from magnetized samples is considered in the general case of arbitrary orientation between the incident polarization, the magnetic field of the sample and the polarization of the scattered neutrons. Including both nuclear and magnetic scattering the general expressions for the cross section and the polarization of the scattered beam are derived in the case of small-angle scattering. It is shown that under certain experimental conditions an effect analogous to the Neutron Spin Echo should be observed, which could be used to measure small energy transfers. The contribution arising from the scattering by spin waves is examined in detail.

Origins of phase anomalies in 13C FT NMR spectra

AbstractSome controversy exists on the origin(s) of phase anomalies observed in 13C FT NMR spectra. Two separate explanations, based on either echo or sampling effects, have been proposed by previous workers. We now show experimentally that these two effects can occur separately or together and, in the latter case, the effects can interfere with one another. Methods to ameliorate or remove phase anomalies are briefly reviewed.

Effect of echo and reverberation of a restricted information capacity on the speech process.

Effect of echo and reverberation of a restricted information capacity on the speech process.

Picosecond tri-transition and two-color photon echoes in a doped molecular solid

Picosecond tri-level photon echoes are generated among vibronic transitions of pentacene doped into a naphthalene host. The echoes are generated with three excitation pulses of which the first one, at ω 1, always excites a vibronic transition in the pentacene molecule. With the second excitation pulse at ω 2 and the third at ω 1, a tri-transition echo (TTE) is formed. With the time ordering of the second and third pulse reversed, a connected two-color stimulated echo (C2CSE) is generated. It is shown that, for small pulse angles, the low-temperature decay, of both echo effects is identical and that a smooth transition of one echo effect into the other occurs at the overlap in time between the second and third excitation pulse. Observation of these echoes further indicates that the inhomogeneous broadening at the selected transitions is strongly correlated.

The “echo effect” and other human resource implications of an Icelandic fishery ban

The paper analyzes the human implications of a shrimp fishery ban in Northwest Iceland in 1978. The significance of the impact revoles around the “echo effect” (which means that the impact is not felt until several seasons after the Ban) and other factors. On a more germane level, this study shows that policies seldom have an immediate impact. Governmental action, moreover, produces short‐term coping mechanism within the fishery. Finally, policies are likely to produce homogenous patterns of production which affect a fisherman's status in his community.

Echo phenomena in plasmas

Various types of echo oscillations in plasmas are discussed. Both unbounded plasmas (gaskinetic plasmas and plasmas in external fields) and bounded plasma systems are considered. Several practical applications of echo effects in radio wave propagation and plasma diagnostics are discussed. The second- and third- order echo oscillations in equilibrium isotropic and magnetized plasmas and in semiconductor plasmas are discussed. A charged-particle beam in a non-equilibrium plasma can lead to an amplification (over time) or a growth (over space) of echo oscillations. A ballistic theory is offered for echos in plasmas. This theory can describe echos in the case of large-amplitude external perturbations, under conditions such that the method of successive approximations cannot be used. The ballistic theory can also describe echo saturation. Echo phenomena in inhomogeneous plasmas are discussed. Section 2 reports a study of echos in bounded plasmas. In this case, additional echo phenomena result from the reflection of charged particles from the plasma boundaries and from the existence of surface waves. Research on echos in plasma slabs and metal films is reviewed. Echo effects can lead to an anomalous transmission of electromagnetic waves through a plasma slab which is opaque (in the linear approximation) to the fields of these waves. Section 3 reviews the basic experimental data on echos in the cyclotron, ion, and plasma zones and research on collisions and microscopic turbulence in plasmas by means of echos. The experimental data available are compared with the theoretical results.

Echo effect in a liquid containing gas bubbles

Acoustic echo is considered for a liquid containing gas bubbles, which is analogous to cyclotron echo in plasma. An analytical calculation is performed on the parameters of the entire series of echo pulses for the case where standing-wave pulses are generated. The addition of a small number of randomly distributed gas bubbles to a liquid substantially alters the dispersion behavior for acoustic oscillation. The physical mechanism responsible is analagous to Landau damping in plasma physics and consists of the wave transmitting it's energy to resonant bubbles, in which the natural frequency of the radial oscillations is close to the wave frequency.

Echo phenomenon associated with lower-hybrid wave launching

Lower-hybrid waves at two different frequencies f1 and f2 are launched simultaneously from two localized antennas, and a third wave is observed to arise near the plasma edge at the frequency f=f2−f1. This phenomenon can be explained by an echo effect near the plasma surface.

Oscillatory behaviour of two-photon echo signals

The two-photon (TP) echo effect has been investigated in a two-level spin system (E′ 1 centres in glassy silica) by revealing the second-harmonic wave emitted by the system. Oscillatory signals were observed when either of the input pulses was long compared to the TP-nutational period.

Detection of atrial septal defect with left-to-right shunt by inferior vena cava contrast echocardiography.

Contrast echocardiography was used before cardiac catheterisation in 37 patients with atrial septal defect and a left-to-right shunt and in 18 patients with a raised right atrial and ventricular pressure to assess the contrast echo effect in the inferior vena cava. Using two dimensional contrast apical echocardiography we found a negative contrast echo effect within the right atrium in many but not all patients with atrial defect. Contrast echoes entering the inferior vena cava during presystole or early to mid-diastole were detected in patients with heart disease causing raised right atrial and ventricular pressures and also in all patients with atrial septal defect. No contrast echo effect in the inferior vena cava was detected in 10 normal subjects. The sensitivity of this contrast pattern in the inferior vena cava in diagnosing atrial septal defect was 100%. When other conditions causing raised right atrial pressure were excluded, the specificity and predictive accuracy were 100% for both. The presystolic contrast echo effect in the inferior vena cava, semiquantitatively graded, correlated with the size of the shunt determined by oximetry. In 20 patients re-examined after the surgical correction of the atrial septal defect, no presystolic contrast echo effect was detected in the inferior vena cava. Contrast echocardiography of the inferior vena cava is a valuable and reliable method for diagnosing atrial septal defect with left-to-right shunt.

Ionic interactions in solutions. V. transference number variation with concentration—contribution to a theoretical interpretation for binary symmetrical electrolytes

The introduction of the echo effect in the conductance functions shows that the variation of transference numbers with concentration is independent of the relaxation field and can be exclusively attributed to electrophoresis. The theoretical expression of transference number variation with concentration is checked by reprocessing literature data. The dependence of the electrophoretic contribution on the distance of approach of two ions of opposite charge is discussed and is found to be independent of the parameters controlling short-range configurations. By combining transference numbers and conductance data, it is possible to get an experimental evaluation of the electrophoretic and relaxation effects which are compared to the corresponding theoretical derivations.

A Model for the Subjective Effects of Listener Echo on Telephone Connections

Any appreciable listener echo on telephone lines is perceived as undesirable, and considerable effort is expended to hold echo to acceptable levels. To provide a basis for appropriately controlling listener echo, a series of four subjective tests was conducted at Bell Laboratories to obtain subjective evaluations of the effects of listener echo on telephone transmission quality. The subjective tests included conditions in which the listener echo-path loss was flat or frequency-shaped by selective filtering. The test results showed that subjective opinions for conditions with the same singing margin (minimum value of echo-path loss) were highly dependent on the frequency shaping. A weighted echo-path loss (WEPL) is defined to provide a weighting on the frequency-shaped test conditions so that subjectively equivalent test conditions have approximately the same levels of WEPL. The results of these subjective tests are used to formulate a model of subjective opinion for use in network planning studies. The resulting listener echo opinion model is incorporated into an existing transmission rating model which encompasses loss, noise, and talker echo. Objectives are proposed for listener echo based on WEPL.