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Tonpilz
The term tonpilz or "acoustic mushroom" may refer to a certain type of underwater electro-acoustic transducer. By sandwiching active (i.e. piezoelectric or magnetostrictive) materials between a light, stiff radiating head mass and a heavy tail mass, the transducer can effectively operate as either a projector (source) or a hydrophone (underwater acoustic receiver). The transducer's size, odd shape, and acoustic projection capabilities have earned it the moniker "tonpilz", from the German words ''Ton'' (tone) and ''Pilz'' (mushroom) and from the figurative similarity. Typically, tonpilz transducers are used in sonar applications. To maximize efficiency, transducers are often placed in arrays: a grid of sometimes hundreds of transducers. This arrangement also allows beamforming and steering. Transducers of this form also lend themselves to compensation against the hydrostatic pressures encountered in sonar, particularly for submarine applications. "Acoustic mushroom" may also ref ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sonar
Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances ( ranging), communicate with or detect objects on or under the surface of the water, such as other vessels. "Sonar" can refer to one of two types of technology: ''passive'' sonar means listening for the sound made by vessels; ''active'' sonar means emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar. Sonar may also be used for robot navigation, and sodar (an upward-looking in-air sonar) is used for atmospheric investigations. The term ''sonar'' is also used for the equipment used to generate and receive the sound. The acoustic frequencies used in sonar systems vary from very low ( infrasonic) to e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electroacoustics (acoustical Engineering)
Acoustical engineering (also known as acoustic engineering) is the branch of engineering dealing with sound and oscillation, vibration. It includes the application of acoustics, the science of sound and vibration, in technology. Acoustical engineers are typically concerned with the design, analysis and control of sound. One goal of acoustical engineering can be the reduction of unwanted noise, which is referred to as noise control. Unwanted noise can have significant impacts on animal and human health and well-being, reduce attainment by students in schools, and cause hearing loss. Noise control principles are implemented into technology and design in a variety of ways, including control by redesigning sound sources, the design of noise barriers, sound absorbers, suppressors, and buffer zones, and the use of hearing protection (earmuffs or earplugs). Besides noise control, acoustical engineering also covers positive uses of sound, such as the use of medical ultrasound, ultrasound ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Piezoelectricity
Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied mechanical stress. The piezoelectric effect results from the linear electromechanical interaction between the mechanical and electrical states in crystalline materials with no inversion symmetry. The piezoelectric effect is a reversible process: materials exhibiting the piezoelectric effect also exhibit the reverse piezoelectric effect, the internal generation of a mechanical strain resulting from an applied electric field. For example, lead zirconate titanate crystals will generate measurable piezoelectricity when their static structure is deformed by about 0.1% of the original dimension. Conversely, those same crystals will change about 0.1% of their static dimension when an external electric field is applied. The inverse piezoelectric effect is used in the pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetostriction
Magnetostriction is a property of magnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of materials' magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ. The effect was first identified in 1842 by James Joule when observing a sample of iron. Magnetostriction applies to magnetic fields, while electrostriction applies to electric fields. Magnetostriction causes energy loss due to frictional heating in susceptible ferromagnetic cores, and is also responsible for the low-pitched humming sound that can be heard coming from transformers, where alternating currents produce a changing magnetic field. Explanation Internally, ferromagnetic materials have a structure that is divided into '' domains'', each of which is a region of uniform magnetization. When a magnetic field is applied, the boundaries between the domains shift and the domains rota ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrophone
A hydrophone () is a microphone designed for underwater use, for recording or listening to underwater sound. Most hydrophones contains a piezoelectric transducer that generates an electric potential when subjected to a pressure change, such as a sound wave. A hydrophone can also detect airborne sounds but is insensitive of them because it is designed to match the acoustic impedance of water, a denser fluid than air. Sound travels 4.3 times faster in water than in air, and a sound wave in water exerts a pressure 60 times more than what is exerted by a wave of the same amplitude in air. Similarly, a standard microphone can be buried in the ground, or immersed in water if it is put in a waterproof container but will give poor performance because of the similarly-bad acoustic impedance match. History The first hydrophones consisted of a tube with a thin membrane covering the submerged end and the observer's ear of the equipment. The design of effective hydrophones must take into a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beamforming
Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an antenna array in such a way that signals at particular angles experience constructive interference while others experience destructive interference. Beamforming can be used at both the transmitting and receiving ends in order to achieve spatial selectivity. The improvement compared with omnidirectional reception/transmission is known as the directivity of the array. Beamforming can be used for radio or sound waves. It has found numerous applications in radar, sonar, seismology, wireless communications, radio astronomy, acoustics and biomedicine. Adaptive beamforming is used to detect and estimate the signal of interest at the output of a sensor array by means of optimal (e.g. least-squares) spatial filtering and interference rejection. Techniques To change the directionality of the array when ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Royal Albert Hall
The Royal Albert Hall is a concert hall on the northern edge of South Kensington, London, England. It has a seating capacity of 5,272. Since the hall's opening by Queen Victoria in 1871, the world's leading artists from many performance genres have appeared on its stage. It is the venue for the BBC Proms concerts, which have been held there every summer since 1941. It is host to more than 390 shows in the main auditorium annually, including classical, rock and pop concerts, ballet, opera, film screenings with live orchestral accompaniment, sports, awards ceremonies, school and community events, and charity performances and banquets. A further 400 events are held each year in the non-auditorium spaces. Over its 153-year history, the hall has hosted people from various fields, including meetings held by suffragettes, speeches from Winston Churchill, Charles de Gaulle, and Albert Einstein, fights by Lennox Lewis, exhibition bouts by Muhammad Ali, and concerts from regular performer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
