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Acoustic Horn
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 horns, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acoustic Impedance
Acoustic impedance and specific acoustic impedance are measures of the opposition that a system presents to the acoustic flow resulting from an acoustic pressure applied to the system. The SI unit of acoustic impedance is the pascal-second per cubic metre (), or in the MKS system the rayl per square metre (), while that of specific acoustic impedance is the pascal-second per metre (), or in the MKS system the rayl. There is a close analogy with electrical impedance, which measures the opposition that a system presents to the electric current resulting from a voltage applied to the system. Mathematical definitions Acoustic impedance For a linear time-invariant system, the relationship between the acoustic pressure applied to the system and the resulting acoustic volume flow rate through a surface perpendicular to the direction of that pressure at its point of application is given by: : p(t) = * Qt), or equivalently by : Q(t) = * pt), where * ''p'' is the acoustic pressure; * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ear Trumpet
An ear trumpet is a tubular or funnel-shaped device which collects sound waves and leads them into the ear. They were used as hearing aids, resulting in a strengthening of the sound energy impact to the eardrum and thus improved hearing for a deaf or hard-of-hearing individual. Ear trumpets were made of sheet metal, silver, wood, snail shells or animal horns. They have largely been replaced in wealthier areas of the world by modern hearing aid technology that is much smaller and less obtrusive, albeit more expensive. A sound trumpet does not "amplify" sound. It takes the sound power received over a large area and concentrates it into a smaller area. The received sound is louder, but no power has been created in the process. History The use of ear trumpets for the partially deaf dates back to the 17th century.Howard, Alexander. "Hearing Aids: Smaller and Smarter." New York Times, November 26, 1998. The earliest description of an ear trumpet was given by the French Jesuit priest a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mole Cricket Burrow
Mole (or Molé) may refer to: Animals * Mole (animal) or "true mole", mammals in the family Talpidae, found in Eurasia and North America * Golden moles, southern African mammals in the family Chrysochloridae, similar to but unrelated to Talpidae moles * Marsupial moles, Australian mammals in the family Notoryctidae, similar to but unrelated to Talpidae moles Other common meanings * Mole, colloquial name for a nevus, a growth on human skin ** Melanocytic nevus, another term for mole * Mole (architecture), a pier, jetty, breakwater, or junction between places separated by water * Mole (espionage), a spy who inserts himself into an organisation in order to spy on it. * Mole (sauce), Mexican sauce made from chili peppers, often including fruits, other spices, or chocolate Arts and entertainment * Adrian Mole, the central character in a series of novels by Sue Townsend * Mole, a main character in the children's novel ''The Wind in the Willows'' by Kenneth Grahame * Mole (Zdeně ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harmonic
A harmonic is a wave with a frequency that is a positive integer multiple of the ''fundamental frequency'', the frequency of the original periodic signal, such as a sinusoidal wave. The original signal is also called the ''1st harmonic'', the other harmonics are known as ''higher harmonics''. As all harmonics are periodic at the fundamental frequency, the sum of harmonics is also periodic at that frequency. The set of harmonics forms a '' harmonic series''. The term is employed in various disciplines, including music, physics, acoustics, electronic power transmission, radio technology, and other fields. For example, if the fundamental frequency is 50 Hz, a common AC power supply frequency, the frequencies of the first three higher harmonics are 100 Hz (2nd harmonic), 150 Hz (3rd harmonic), 200 Hz (4th harmonic) and any addition of waves with these frequencies is periodic at 50 Hz. In music, harmonics are used on string instruments and wind instrum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Musical Note
In music, a note is the representation of a musical sound. Notes can represent the Pitch (music), pitch and Duration (music), duration of a sound in musical notation. A note can also represent a pitch class. Notes are the building blocks of much written music: musical analysis#Discretization, discretizations of musical phenomena that facilitate performance, comprehension, and musical analysis, analysis. The term ''note'' can be used in both generic and specific senses: one might say either "the piece 'Happy Birthday to You' begins with two notes having the same pitch", or "the piece begins with two repetitions of the same note". In the former case, one uses ''note'' to refer to a specific musical event; in the latter, one uses the term to refer to a class of events sharing the same pitch. (See also: Key signature names and translations.) Two notes with fundamental frequency, fundamental frequencies in a ratio equal to any integer power of two (e.g., half, twice, or four times ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standing Wave
In physics, a standing wave, also known as a stationary wave, is a wave that oscillates in time but whose peak amplitude profile does not move in space. The peak amplitude of the wave oscillations at any point in space is constant with respect to time, and the oscillations at different points throughout the wave are in phase. The locations at which the absolute value of the amplitude is minimum are called nodes, and the locations where the absolute value of the amplitude is maximum are called antinodes. Standing waves were first noticed by Michael Faraday in 1831. Faraday observed standing waves on the surface of a liquid in a vibrating container. Franz Melde coined the term "standing wave" (German: ''stehende Welle'' or ''Stehwelle'') around 1860 and demonstrated the phenomenon in his classic experiment with vibrating strings. This phenomenon can occur because the medium is moving in the direction opposite to the movement of the wave, or it can arise in a stationary medium ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sound Pressure
Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydrophone. The SI unit of sound pressure is the pascal (Pa). Mathematical definition A sound wave in a transmission medium causes a deviation (sound pressure, a ''dynamic'' pressure) in the local ambient pressure, a ''static'' pressure. Sound pressure, denoted ''p'', is defined by p_\text = p_\text + p, where * ''p''total is the total pressure, * ''p''stat is the static pressure. Sound measurements Sound intensity In a sound wave, the complementary variable to sound pressure is the particle velocity. Together, they determine the sound intensity of the wave. ''Sound intensity'', denoted I and measured in W· m−2 in SI units, is defined by \mathbf I = p \mathbf v, where * ''p'' is the sound pressure, * v is the particle velocity. Acoustic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mid-range Speaker
A mid-range speaker is a loudspeaker driver that reproduces sound in the frequency range from 250 to 2000 Hz. It is also known as a squawker. Mid-range drivers are usually cone types or, less commonly, dome types, or compression horn drivers. The radiating diaphragm of a cone mid-range unit is a truncated cone, with a voice coil attached at the neck, along with the spider portion of the suspension, and with the cone surround at the wide end. Cone mid-range drivers typically resemble small woofers. The most common material used for mid-range cones is paper, occasionally impregnated and/or surface-treated with polymers or resins in order to improve vibrational damping. Other mid-range cone materials include plastics such as polypropylene, Cobex, Bextrene, woven Kevlar, fiberglass, carbon fiber, or light metal alloys based on aluminium, magnesium, titanium, or other alloys. The radiating surface of a dome mid-range is typically a 90-degree section of a sphere, made from cloth, metal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tweeter
A tweeter or treble speaker is a special type of loudspeaker (usually dome, inverse dome or horn-type) that is designed to produce high audio frequencies, typically deliver high frequencies up to 100 kHz. The name is derived from the high pitched sounds made by some birds (tweets), especially in contrast to the low woofs made by many dogs, after which low-frequency drivers are named (woofers). Operation Nearly all tweeters are electrodynamic drivers using a voice coil suspended within a fixed magnetic field. These designs operate by applying current from the output of an amplifier circuit to a coil of wire called a voice coil. The voice coil produces a varying magnetic field, which works against the fixed magnetic field of a permanent magnet around which the cylindrical voice coil is suspended, forcing the voice coil and the diaphragm attached to it to move. This mechanical movement resembles the waveform of the electronic signal supplied from the amplifier's output ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phonograph
A phonograph, in its later forms also called a gramophone (as a trademark since 1887, as a generic name in the UK since 1910) or since the 1940s called a record player, or more recently a turntable, is a device for the mechanical and analogue recording and reproduction of sound. The sound vibration waveforms are recorded as corresponding physical deviations of a spiral groove engraved, etched, incised, or impressed into the surface of a rotating cylinder or disc, called a "record". To recreate the sound, the surface is similarly rotated while a playback stylus traces the groove and is therefore vibrated by it, very faintly reproducing the recorded sound. In early acoustic phonographs, the stylus vibrated a diaphragm which produced sound waves which were coupled to the open air through a flaring horn, or directly to the listener's ears through stethoscope-type earphones. The phonograph was invented in 1877 by Thomas Edison. Alexander Graham Bell's Volta Laboratory made s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foghorn
A foghorn or fog signal is a device that uses sound to warn vehicles of navigational hazards such as rocky coastlines, or boats of the presence of other vessels, in foggy conditions. The term is most often used in relation to marine transport. When visual navigation aids such as lighthouses are obscured, foghorns provide an audible warning of rock outcrops, shoals, headlands, or other dangers to shipping. Description All foghorns use a vibrating column of air to create an audible tone, but the method of setting up this vibration differs. Some horns, such as the Daboll trumpet, used vibrating plates or metal reeds, a similar principle to a modern electric car horn. Others used air forced through holes in a rotating cylinder or disk, in the same manner as a siren. Semi-automatic operation of foghorns was achieved by using a clockwork mechanism (or "coder") to sequentially open the valves admitting air to the horns; each horn was given its own timing characteristics to help marine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
