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Megaphone
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 Since the 1960s the voice-powered ''acoustic megaphone'' described above has been replaced by the ''electric megaphone'', which uses a microphone, an electrically-powered amplifier and a folded horn loudsp ... [...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] |
Microphone
A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public events, motion picture production, live and recorded audio engineering, sound recording, two-way radios, megaphones, and radio and television broadcasting. They are also used in computers for recording voice, speech recognition, VoIP, and for other purposes such as ultrasonic sensors or knock sensors. Several types of microphone are used today, which employ different methods to convert the air pressure variations of a sound wave to an electrical signal. The most common are the dynamic microphone, which uses a coil of wire suspended in a magnetic field; the condenser microphone, which uses the vibrating diaphragm as a capacitor plate; and the contact microphone, which uses a crystal of piezoelectric material. Microphones typically n ... [...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] |
Horn (acoustic)
An acoustic horn or waveguide is a tapered sound guide designed to provide an acoustic impedance match between a sound source and free air. This has the effect of maximizing the efficiency with which sound waves from the particular source are transferred to the air. Conversely, a horn can be used at the receiving end to optimize the transfer of sound from the air to a receiver. Acoustic horns are found in nature in the form of the burrows constructed by male mole crickets to amplify their song. The earliest appearance of the horn in connection to sound in The Times was published in 1786: Applications Acoustic horns are used in: * horn loudspeakers * brass and woodwind musical instruments * vehicle horns such as those used on cars, trucks, trains, boats, and bicycles * megaphones, often used by lifeguards at public swimming pools. * foghorns, used to warn ships * ear horns, used by people who are hard of hearing (the human ear itself having the form of a horn) * pickup horn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Samuel Morland
Sir Samuel Morland, 1st Baronet (1625 – 30 December 1695), or Moreland, was an English academic, diplomat, spy, inventor and mathematician of the 17th century, a polymath credited with early developments in relation to computing, hydraulics and steam power. Education The son of Thomas Morland, the rector of Sulhamstead Bannister in Berkshire, he was educated at Winchester College and Magdalene College, Cambridge, where he became a Fellow in 1649. Devoting much time to the study of mathematics, Morland also became an accomplished Latinist and was proficient in Greek, Hebrew and French – then the language of culture and diplomacy. While a tutor at Cambridge, he first encountered Samuel Pepys who became a lifelong acquaintance. Diplomat A keen follower of public affairs, he left Cambridge and entered public service. He undertook a trip to Sweden in 1653, and in 1655 was sent by Oliver Cromwell on a mission to Italy to protest at actions taken against the Waldensians by the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loudspeaker
A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or "loudspeaker", comprises one or more such speaker ''drivers'', an enclosure, and electrical connections possibly including a crossover network. The speaker driver can be viewed as a linear motor attached to a diaphragm which couples that motor's movement to motion of air, that is, sound. An audio signal, typically from a microphone, recording, or radio broadcast, is amplified electronically to a power level capable of driving that motor in order to reproduce the sound corresponding to the original unamplified electronic signal. This is thus the opposite function to the microphone; indeed the ''dynamic speaker'' driver, by far the most common type, is a linear motor in the same basic configuration as the dynamic microphone which uses such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Athanasius Kircher
Athanasius Kircher (2 May 1602 – 27 November 1680) was a German Jesuit scholar and polymath A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose knowledge spans a substantial number of subjects, known to draw on complex bodies of knowledge to solve specific pro ... who published around 40 major works, most notably in the fields of comparative religion, geology, and medicine. Kircher has been compared to fellow Jesuit Roger Joseph Boscovich and to Leonardo da Vinci for his enormous range of interests, and has been honoured with the title "Master of a Hundred Arts".Woods, p. 108. He taught for more than 40 years at the Roman College, where he set up a wunderkammer. A resurgence of interest in Kircher has occurred within the scholarly community in recent decades. Kircher claimed to have deciphered the Egyptian hieroglyphs, hieroglyphic writing of the ancient Egyptian language, but most of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Impedance Matching
In electronics, impedance matching is the practice of designing or adjusting the input impedance or output impedance of an electrical device for a desired value. Often, the desired value is selected to maximize power transfer or minimize signal reflection. For example, impedance matching typically is used to improve power transfer from a radio transmitter via the interconnecting transmission line to the antenna. Signals on a transmission line will be transmitted without reflections if the transmission line is terminated with a matching impedance. Techniques of impedance matching include transformers, adjustable networks of lumped resistance, capacitance and inductance, or properly proportioned transmission lines. Practical impedance-matching devices will generally provide best results over a specified frequency band. The concept of impedance matching is widespread in electrical engineering, but is relevant in other applications in which a form of energy, not necessarily el ... [...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] |
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] |
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] |
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