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Bullhorn
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 Since the 1960s the voice-powered ''acoustic megaphone'' described above has been replaced by the ''electric megaphone'', which uses a microphone, an electrically-powered amplifier and a folded horn loudspe ... [...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] |
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] |
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 that will flow through an external electric circuit to the positive terminal. When a battery is connected to an external electric load, a redox reaction converts high-energy reactants 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 materials are irreversibly changed during discharge; a common example is the alkaline battery used ... [...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 signals. Audio signals have frequencies in the audio frequency range of roughly 20 to 20,000 Hz, which corresponds to the lower and upper limits of human hearing. Audio signals may be synthesized directly, or may originate at a transducer such as a microphone, 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 storage device or mixing console, used in operations such as multi-track recording and sound reinforcement. Signal flow Signal flow is the path an audio signal will take from source to the sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Austrian People
, pop = 8–8.5 million , regions = 7,427,759 , region1 = , pop1 = 684,184 , ref1 = , region2 = , pop2 = 345,620 , ref2 = , region3 = , pop3 = 197,990 , ref3 = , region4 = , pop4 = 40,300–65,090 , ref4 = , region5 = , pop5 = 45,530 , ref5 = , region6 = , pop6 = 21,600–25,000 , ref6 = , region7 = , pop7 = 20,000 , ref7 = , region8 = , pop8 = 16,331 , ref8 = , region9 = , pop9 = 15,771 , ref9 = , region10 = , pop10 = 14,000 , ref10 = , region11 = , pop11 = 12,000 , ref11 = , region12 = , pop12 = 10,000 , ref12 = , region13 = , pop13 = 9,800 , ref13 = , region14 = , pop14 = 9,044 , ref14 = , region15 = , pop15 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bugle
The bugle is one of the simplest brass instruments, normally having no valves or other pitch-altering devices. All pitch control is done by varying the player's embouchure. History The bugle developed from early musical or communication instruments made of animal horns, with the word "bugle" itself coming from "buculus", Latin for bullock (castrated bull). The earliest bugles were shaped in a coil – typically a double coil, but also a single or triple coil – similar to the modern horn, and were used to communicate during hunts and as announcing instruments for coaches (somewhat akin to today's automobile horn). Predecessors and relatives of the bugle included the post horn, the Pless horn (sometimes called the "Prince Pless horn"), the bugle horn, and the shofar, among others. The ancient Roman army used the buccina. The first verifiable formal use of a brass bugle as a military signal device was the ''Halbmondbläser'', or half-moon bugle, used in Hanover in 1758. I ... [...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 CPR/ 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 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, although they can also be volunteers. The conditions resulting in drowning are summarized by the 'drowning ... [...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 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, dance, jumps, cheers, and stunting. Modern cheerleading is very closely associated with American football and basketball. Sports such as association football (soccer), ice hockey, volleyball, baseball, and wrestling will sometimes sponsor cheerleading squads. The ICC Twenty20 Cricket World Cup in South Africa in 2007 was the first international cricket event to have cheerleaders. The Florida Marlins were the first Major League Baseball team to have a cheerleading team. Cheerleading originated as an all-male activity in the United States, and remains predominantly in America, with an e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thomas Edison
Thomas Alva Edison (February 11, 1847October 18, 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 light bulb, have had a widespread impact on the modern 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 laboratory in Fort Myers, Florida, in co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MOHAI - Firefighter's Speaking Trumpet 01A
The Museum of History & Industry (MOHAI) is a history museum in the South Lake Union neighborhood of Seattle, Washington, United States. It is the largest private heritage organization in Washington state, maintaining a collection of nearly four million artifacts, photographs, and archival materials primarily focusing on Seattle and the greater Puget Sound region. A portion of this collection (roughly 2% at any given time) is on display in the museum's galleries at the historic Naval Reserve Armory in Lake Union Park. The museum's keynote exhibits include: Boeing's first commercial plane, the 1919 Boeing B-1; the Petticoat Flag, a U.S. flag sewn by women during the 1856 Battle of Seattle; and the Rainier Brewing Company's 12-foot tall neon "R" sign. In addition to both permanent and temporary exhibits, MOHAI administers ongoing youth and adult programming, and regularly hosts public events in partnership with other community organizations, particularly within the South Lake U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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