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The MP3 lossy audio data compression algorithm takes advantage of a perceptual limitation of human hearing called auditory masking. In 1894, the American physicist Alfred M. Mayer reported that a tone could be rendered inaudible by another tone of lower frequency. In 1959, Richard Ehmer described a complete set of auditory curves regarding this phenomenon. Ernst Terhardt et al. created an algorithm describing auditory masking with high accuracy. This work added to a variety of reports from authors dating back to Fletcher, and to the work that initially determined critical ratios and critical bandwidths.
When were audio curves described by Richard Ehmer?
A: 1959

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The Great Plains come to an abrupt end at the Rocky Mountains. The Rocky Mountains form a large portion of the Western U.S., entering from Canada and stretching nearly to Mexico. The Rocky Mountain region is the highest region of the United States by average elevation. The Rocky Mountains generally contain fairly mild slopes and wider peaks compared to some of the other great mountain ranges, with a few exceptions (such as the Teton Mountains in Wyoming and the Sawatch Range in Colorado). The highest peaks of the Rockies are found in Colorado, the tallest peak being Mount Elbert at 14,440 ft (4,400 m). The Rocky Mountains contain some of the most spectacular, and well known scenery in the world. In addition, instead of being one generally continuous and solid mountain range, it is broken up into a number of smaller, intermittent mountain ranges, forming a large series of basins and valleys.
The appellation Mountains are the highest region of what?
A: unanswerable

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In 1978, Sewall Wright suggested that human populations that have long inhabited separated parts of the world should, in general, be considered different subspecies by the usual criterion that most individuals of such populations can be allocated correctly by inspection. Wright argued that it does not require a trained anthropologist to classify an array of Englishmen, West Africans, and Chinese with 100% accuracy by features, skin color, and type of hair despite so much variability within each of these groups that every individual can easily be distinguished from every other. However, it is customary to use the term race rather than subspecies for the major subdivisions of the human species as well as for minor ones.
What is required to allocate individuals in subspecies populations correctly?
A: inspection

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During the celebration, theaters called tablados are built in many places throughout the cities, especially in Montevideo. Traditionally formed by men and now starting to be open to women, the different Carnival groups (Murgas, Lubolos or Parodistas) perform a kind of popular opera at the tablados, singing and dancing songs that generally relate to the social and political situation. The 'Calls' groups, basically formed by drummers playing the tamboril, perform candombe rhythmic figures. Revelers wear their festival clothing. Each group has its own theme. Women wearing elegant, bright dresses are called vedettes and provide a sensual touch to parades.
What do the different Carnival groups perform together?
A:
opera