Acoustic Supercoupling in a Zero-Compressibility Waveguide

Funneling acoustic waves through largely mismatched channels is of fundamental importance to tailor and transmit sound for a variety of applications. In electromagnetics, zero-permittivity metamaterials have been used to enhance the coupling of energy in and out of ultranarrow channels, based on a phenomenon known as supercoupling. These metamaterial channels can support total transmission and complete phase uniformity, independent of the channel length, despite being geometrically mismatched to their input and output ports. In the field of acoustics, this phenomenon is challenging to achieve, since it requires zero-density metamaterials, typically realized with waveguides periodically loaded with membranes or resonators. Compared to electromagnetics, the additional challenge is due to the fact that conventional acoustic waveguides do not support a cut-off for the dominant mode of propagation, and therefore zero-index can be achieved only based on a collective resonance of the loading elements. Here we propose and experimentally realize acoustic supercoupling in a dual regime, using a compressibility-near-zero acoustic channel. Rather than engineering the channel with subwavelength inclusions, we operate at the cut-off of a higher-order acoustic mode, demonstrating the realization and efficient excitation of a zero-compressibility waveguide with effective soft boundaries. We experimentally verify strong transmission through a largely mismatched channel and uniform phase distribution, independent of the channel length. Our results open interesting pathways towards the realization of extreme acoustic parameters, and their implementation in relevant applications, such as ultrasound imaging, sonar technology, and sound transmission

Taxation - Federal Income Tax - Meals and Lodging Under the 1954 Code

Before discussing the application of the 1954 Internal Revenue Code with regard to the taxability of meals and lodging furnished an employee by his employer, several fundamental tax concepts should be examined. The first of these involves the definition of gross income, which for many years has been cast in broad statutory language. For example, section 22(a) of the 1939 Internal Revenue Code provided that gross income includes ... gains, profits, and income derived from salaries, wages, or compensation for personal service ... of whatever kind and in whatever form paid .... Comprehensive as these terms appear, gross income has not been interpreted to include all forms of economic benefits received by a taxpayer. Traditionally, for reasons both of policy and administration, the net use value of goods and services owned and used by a taxpayer for his own benefit had been excluded. Similarly, the differential value of improved working conditions is not generally considered to give rise to taxable income. Although better working conditions may have economic value in the eyes of an employee and can exert substantial in influence on the rates of ordinary compensation, most non-cash benefits in this sphere have been tax exempt. The main problems, however, have not arisen in the theoretical definition of income but in classifying particular fact situations. Under what circumstances should the value of meals and lodging furnished by an employer to his employees be excluded

Developmental changes in reasoning about cross-classified individuals.

Social categories allow children to make inferences about novel situations, which can then guide their interactions with others. However, this process can be complicated because individuals often belong to many different, sometimes interrelated, social categories. Four experiments examine whether children and adults differ in their willingness to classify a person as holding two social roles (e.g., a mother and a daughter), and how this influences their reasoning. Specifically, this work will examine the influence of cross-classification on inductive inferences, trust in testimony, and knowledge evaluations. The aim of these experiments is to investigate whether children privilege certain roles when reasoning about individuals who hold multiple social roles. Because children rely heavily on their knowledge of individuals’ social roles to interact with them appropriately, it is important that children be able to accurately use these social categories to reason about others. Experiments 1 and 2 explore children’s willingness to cross-classify individuals into a variety of social roles with varying degrees of hierarchical (vs. non-hierarchical) structure. Experiment 2 further examines what cognitive mechanisms may underlie children’s cross-classification behaviors. Experiments 3 and 4 examine how children make inferences about and evaluate the testimony of cross-classified individuals. Overall, the findings of these four experiments illustrate that there are developmental differences in willingness to cross-classify and reasoning about cross-classified individuals occurring between the preschool, early elementary, and adult years. The results of these experiments suggest that cross-classification may influence the way children make inferences about individuals, but that cross-classification does not influence their trust in the testimony of individuals with multiple social roles. This work contributes to our growing understanding of how children utilize information about social categories to reason about others

Survival of fossils under extreme shocks induced by hypervelocity impacts

Experimental data are shown for survival of fossilized diatoms undergoing shocks in the GPa range. The results were obtained from hypervelocity impact experiments which fired fossilized diatoms frozen in ice into water targets. After the shots, the material recovered from the target water was inspected for diatom fossils. Nine shots were carried out, at speeds from 0.388 to 5.34?km?s?1, corresponding to mean peak pressures of 0.2–19?GPa. In all cases, fragmented fossilized diatoms were recovered, but both the mean and the maximum fragment size decreased with increasing impact speed and hence peak pressure. Examples of intact diatoms were found after the impacts, even in some of the higher speed shots, but their frequency and size decreased significantly at the higher speeds. This is the first demonstration that fossils can survive and be transferred from projectile to target in hypervelocity impacts, implying that it is possible that, as suggested by other authors, terrestrial rocks ejected from the Earth by giant impacts from space, and which then strike the Moon, may successfully transfer terrestrial fossils to the Moon

Ambient Sound Provides Supervision for Visual Learning

The sound of crashing waves, the roar of fast-moving cars -- sound conveys important information about the objects in our surroundings. In this work, we show that ambient sounds can be used as a supervisory signal for learning visual models. To demonstrate this, we train a convolutional neural network to predict a statistical summary of the sound associated with a video frame. We show that, through this process, the network learns a representation that conveys information about objects and scenes. We evaluate this representation on several recognition tasks, finding that its performance is comparable to that of other state-of-the-art unsupervised learning methods. Finally, we show through visualizations that the network learns units that are selective to objects that are often associated with characteristic sounds.Comment: ECCV 201

Visually Indicated Sounds

Objects make distinctive sounds when they are hit or scratched. These sounds reveal aspects of an object's material properties, as well as the actions that produced them. In this paper, we propose the task of predicting what sound an object makes when struck as a way of studying physical interactions within a visual scene. We present an algorithm that synthesizes sound from silent videos of people hitting and scratching objects with a drumstick. This algorithm uses a recurrent neural network to predict sound features from videos and then produces a waveform from these features with an example-based synthesis procedure. We show that the sounds predicted by our model are realistic enough to fool participants in a "real or fake" psychophysical experiment, and that they convey significant information about material properties and physical interactions

Statistics of natural reverberation enable perceptual separation of sound and space

In everyday listening, sound reaches our ears directly from a source as well as indirectly via reflections known as reverberation. Reverberation profoundly distorts the sound from a source, yet humans can both identify sound sources and distinguish environments from the resulting sound, via mechanisms that remain unclear. The core computational challenge is that the acoustic signatures of the source and environment are combined in a single signal received by the ear. Here we ask whether our recognition of sound sources and spaces reflects an ability to separate their effects and whether any such separation is enabled by statistical regularities of real-world reverberation. To first determine whether such statistical regularities exist, we measured impulse responses (IRs) of 271 spaces sampled from the distribution encountered by humans during daily life. The sampled spaces were diverse, but their IRs were tightly constrained, exhibiting exponential decay at frequency-dependent rates: Mid frequencies reverberated longest whereas higher and lower frequencies decayed more rapidly, presumably due to absorptive properties of materials and air. To test whether humans leverage these regularities, we manipulated IR decay characteristics in simulated reverberant audio. Listeners could discriminate sound sources and environments from these signals, but their abilities degraded when reverberation characteristics deviated from those of real-world environments. Subjectively, atypical IRs were mistaken for sound sources. The results suggest the brain separates sound into contributions from the source and the environment, constrained by a prior on natural reverberation. This separation process may contribute to robust recognition while providing information about spaces around us