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Megaphone
A megaphone, speaking trumpet, bullhorn, blowhorn, or loudhailer is usually a portable or hand-held, cone-shaped horn (acoustic), acoustic horn used to amplifier, amplify a person's voice or other sounds and direct it in a given direction. The sound is introduced into the narrow end of the megaphone, by holding it up to the face and speaking into it, and the sound waves radiate out the wide end. A megaphone increases the volume of sound by increasing the acoustic impedance seen by the vocal cords, impedance matching, matching the impedance of the vocal cords to the air, so that more sound power is radiated. It also serves to direct the sound waves in the direction the horn is pointing. It somewhat distorts the sound of the voice because the frequency response of the megaphone is greater at higher sound frequency, frequencies. Since the 1960s the voice-powered ''acoustic megaphone'' described above has been replaced by the ''electric megaphone'', which uses a microphone, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Megaphone Toa
A megaphone, speaking trumpet, bullhorn, blowhorn, or loudhailer is usually a portable or hand-held, cone-shaped acoustic horn used to amplify a person's voice or other sounds and direct it in a given direction. The sound is introduced into the narrow end of the megaphone, by holding it up to the face and speaking into it, and the sound waves radiate out the wide end. A megaphone increases the volume of sound by increasing the acoustic impedance seen by the vocal cords, matching the impedance of the vocal cords to the air, so that more sound power is radiated. It also serves to direct the sound waves in the direction the horn is pointing. It somewhat distorts the sound of the voice because the frequency response of the megaphone is greater at higher sound frequencies. Since the 1960s the voice-powered ''acoustic megaphone'' described above has been replaced by the ''electric megaphone'', which uses a microphone, an electrically-powered amplifier and a folded horn louds ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Public Address System
A public address system (or PA system) is an electronic system comprising microphones, amplifiers, loudspeakers, and related equipment. It increases the apparent volume (loudness) of a human voice, musical instrument, or other acoustic sound source or recorded sound or music. PA systems are used in any public venue that requires that an announcer, performer, etc. be sufficiently audible at a distance or over a large area. Typical applications include sports stadiums, public transportation vehicles and facilities, and live or recorded music venues and events. A PA system may include multiple microphones or other sound sources, a mixing console to combine and modify multiple sources, and multiple amplifiers and loudspeakers for louder volume or wider distribution. Simple PA systems are often used in small venues such as school auditoriums, churches, and small bars. PA systems with many speakers are widely used to make announcements in public, institutional and commercial buildings ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horn Loudspeaker
A horn loudspeaker is a loudspeaker or loudspeaker element which uses an horn (acoustic), acoustic horn to increase the overall efficiency of the driving element(s). A common form ''(right)'' consists of a compression driver which produces sound waves with a small metal diaphragm vibrated by an electromagnet, attached to a horn, a flaring duct to conduct the sound waves to the open air. Another type is a woofer driver mounted in a loudspeaker enclosure which is divided by internal partitions to form a zigzag flaring duct which functions as a horn; this type is called a ''folded horn'' speaker. The horn serves to improve the coupling efficiency between the speaker driver and the air. The horn can be thought of as an "acoustic transformer" that provides impedance matching between the relatively density, dense diaphragm material and the less-dense air. The result is greater acoustic output power from a given driver. The narrow part of the horn next to the driver is called the "throat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Codex Canadensis
''Codex canadensis'' is a handwritten and hand-drawn document from that depicts the wildlife and native peoples of Canada. It contains 180 drawings of First Nations' people, plants, mammals, birds and fish of the New World. Although the manuscript was neither signed nor dated, scholars believe its most likely author was Louis Nicolas, a French Jesuit. It is currently kept at the Gilcrease Museum, in Tulsa, Oklahoma. Author When a facsimile of the Codex was produced in 1934, a foreword by Baron Marc de Villiers attributed the original work to Bécart de Granville. Scholars have more recently discovered that the author was probably Nicolas. The ''Histoire Naturelle des Indes Occidentales'', a document held at the Bibliothèque nationale de France in Paris, is speculated to have also been written by Nicolas and provides an in depth description of the animals, fish and plants of Canada, which are all depicted in the ''Codex Canadensis''. The author of the ''Histoire Naturelle'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Battery (electricity)
An electric battery is a source of electric power consisting of one or more electrochemical cells with external connections for powering electrical devices. When a battery is supplying power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons. When a battery is connected to an external electric load, those negatively charged electrons flow through the circuit and reach the positive terminal, thus causing a redox reaction by attracting positively charged ions, or cations. Thus, higher energy reactants are converted to lower energy products, and the free-energy difference is delivered to the external circuit as electrical energy. Historically the term "battery" specifically referred to a device composed of multiple cells; however, the usage has evolved to include devices composed of a single cell. Primary (single-use or "disposable") batteries are used once and discarded, as the electrode mat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audio Signal
An audio signal is a representation of sound, typically using either a changing level of electrical voltage for analog signals or a series of binary numbers for Digital signal (signal processing), digital signals. Audio signals have frequencies in the audio frequency range of roughly 20 to 20,000 Hz, which corresponds to the lower and upper Human hearing range, limits of human hearing. Audio signals may be Synthesizer, synthesized directly, or may originate at a transducer such as a microphone, Pickup (music technology), musical instrument pickup, phonograph cartridge, or tape head. Loudspeakers or headphones convert an electrical audio signal back into sound. Digital audio systems represent audio signals in a variety of digital formats.Hodgson, Jay (2010). ''Understanding Records'', p.1. . An audio channel or audio track is an audio signal communications channel in a data storage device, storage device or mixing console. It is used in operations such as multi-track recordi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Austrian People
Austrians (, ) are the citizens and Nationality, nationals of Austria. The English term ''Austrians'' was applied to the population of Archduchy of Austria, Habsburg Austria from the 17th or 18th century. Subsequently, during the 19th century, it referred to the citizens of the Empire of Austria (1804–1867), and from 1867 until 1918 to the citizens of Cisleithania. In the closest sense, the name of Austria, term ''Austria'' originally referred to the historical March of Austria, corresponding roughly to the Vienna Basin in what is today Lower Austria. Historically, Austrians were regarded as Germans and viewed themselves as such. The Austrian lands (including Bohemia) were part of the Holy Roman Empire and the German Confederation until the Austro-Prussian War in 1866 which resulted in Kingdom of Prussia, Prussia expelling the Austrian Empire from the Confederation. Thus, when German Empire, Germany was Unification of Germany, founded as a nation-state in 1871, Austria Ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Firefighter
A firefighter (or fire fighter or fireman) is a first responder trained in specific emergency response such as firefighting, primarily to control and extinguish fires and respond to emergencies such as hazardous material incidents, medical incidents, and emergencies that require response from the public that threaten life, property and the environment, as well as to rescue persons from confinement or dangerous situations and preserve evidence. Firefighters may also provide ordinance regulations, safety requirements, and administrative public functions for the communities and areas they are subject to jurisdiction to. Male firefighters are sometimes referred to as firemen (and, less commonly, female firefighters as firewomen). The fire department, also known in some countries as the fire brigade or fire service, is one of the three main emergency services. From urban areas to aboard ships, firefighters have become ubiquitous around the world. The skills required for safe oper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lifeguard
A lifeguard is a rescuer who supervises the safety and rescue of swimmers, surfers, and other water sports participants such as in a swimming pool, water park, beach, spa, river and lake. Lifeguards are trained in swimming and Cardiopulmonary resuscitation, CPR/Automated external defibrillator, AED first aid, certified in water rescue using a variety of aids and equipment depending on requirements of their particular venue. In some areas, lifeguards are part of the emergency services system to incidents and in some communities, lifeguards may function as the primary Emergency medical service, EMS provider. Responsibilities A lifeguard is responsible for the safety of people in an area of water, and usually a defined area immediately surrounding or adjacent to it, such as a beach next to an ocean or lake. The priority is to ensure no harm comes to users of the area for which they are responsible. Lifeguards often take on this responsibility upon employment, However, there ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cheerleading
Cheerleading is an activity in which the participants (called cheerleaders) cheer for their team as a form of encouragement. It can range from chanting slogans to intense Physical exercise, physical activity. It can be performed to motivate sports teams, to entertain the audience, or for competition. Cheerleading routines typically range anywhere from one to three minutes, and contain components of Tumbling (gymnastics), tumbling, dance, List of cheerleading jumps, jumps, cheering, cheers, and List of cheerleading stunts, stunting. Cheerleading originated in the United States, where it has become a tradition. It is less prevalent in the rest of the world, except via its association with American sports or organized cheerleading contests. Modern cheerleading is very closely associated with American football and basketball. Sports such as association football (soccer), ice hockey, volleyball, baseball, and Scholastic wrestling, wrestling will sometimes sponsor cheerleading squad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thomas Edison
Thomas Alva Edison (February11, 1847October18, 1931) was an American inventor and businessman. He developed many devices in fields such as electric power generation, mass communication, sound recording, and motion pictures. These inventions, which include the phonograph, the motion picture camera, and early versions of the electric Incandescent light bulb, light bulb, have had a widespread impact on the modern industrial society, industrialized world. He was one of the first inventors to apply the principles of organized science and teamwork to the process of invention, working with many researchers and employees. He established the first industrial research laboratory. Edison was raised in the American Midwest. Early in his career he worked as a telegraph operator, which inspired some of his earliest inventions. In 1876, he established his first laboratory facility in Menlo Park, New Jersey, where many of his early inventions were developed. He later established a botanical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tiwanaku
Tiwanaku ( or ) is a Pre-Columbian archaeological site in western Bolivia, near Lake Titicaca, about 70 kilometers from La Paz, and it is one of the largest sites in South America. Surface remains currently cover around 4 square kilometers and include decorated ceramics, monumental structures, and megalithic blocks. It has been conservatively estimated that the site was inhabited by 10,000 to 20,000 people in AD 800. The site was first recorded in written history in 1549 by Spanish conquistador Pedro Cieza de León while searching for the southern Inca capital of Qullasuyu. Jesuit chronicler of Peru Bernabé Cobo reported that Tiwanaku's name once was ''taypiqala'', which is Aymara meaning "stone in the center", alluding to the belief that it lay at the center of the world. The name by which Tiwanaku was known to its inhabitants may have been lost as they had no written language. Heggarty and Beresford-Jones suggest that the Puquina language is most likely to have been the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
