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Savart Wheel
The Savart wheel is an acoustical device named after the French physicist Félix Savart (1791–1841), which was originally conceived and developed by the English scientist Robert Hooke (1635–1703). A card held to the edge of a spinning toothed wheel will produce a tone whose pitch varies with the speed of the wheel. A mechanism of this sort, made using brass wheels, allowed Hooke to produce sound waves of a known frequency, and to demonstrate to the Royal Society in 1681 how pitch relates to frequency. For practical purposes Hooke's device was soon supplanted by the invention of the tuning fork. About a century and a half after Hooke's work, the mechanism was taken up again by Savart for his investigations into the range of human hearing. In the 1830s Savart was able to construct large, finely-toothed brass wheels producing frequencies of up to 24 kHz that seem to have been the world's first artificial ultrasonic generators. In the later 19th century, Savart's wheels were a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Samuel Pepys
Samuel Pepys (; 23 February 1633 – 26 May 1703) was an English diarist and naval administrator. He served as administrator of the Royal Navy and Member of Parliament and is most famous for the diary he kept for a decade. Pepys had no maritime experience, but he rose to be the Chief Secretary to the Admiralty under both King Charles II and King James II through patronage, diligence, and his talent for administration. His influence and reforms at the Admiralty were important in the early professionalisation of the Royal Navy. The detailed private diary that Pepys kept from 1660 until 1669 was first published in the 19th century and is one of the most important primary sources for the English Restoration period. It provides a combination of personal revelation and eyewitness accounts of great events, such as the Great Plague of London, the Second Dutch War, and the Great Fire of London. Early life Pepys was born in Salisbury Court, Fleet Street, London, on 23 Febru ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siren (acoustics)
A siren is a loud noise-making device. Civil defense sirens are mounted in fixed locations and used to warn of natural disasters or attacks. Sirens are used on emergency service vehicles such as ambulances, police cars, and fire engines. There are two general types: mechanical and electronic. Many fire sirens (used for calling the volunteer fire fighters) serve double duty as tornado or civil defense sirens, alerting an entire community of impending danger. Most fire sirens are either mounted on the roof of a fire station or on a pole next to the fire station. Fire sirens can also be mounted on or near government buildings, on tall structures such as water towers, as well as in systems where several sirens are distributed around a town for better sound coverage. Most fire sirens are single tone and mechanically driven by electric motors with a rotor attached to the shaft. Some newer sirens are electronically driven speakers. Fire sirens are often called "fire whistles", "fire ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Robison (physicist)
John Robison FRSE (4 February 1739 – 30 January 1805) was a British physicist and mathematician. He was a professor of natural philosophy (the precursor of natural science) at the University of Edinburgh. A member of the Edinburgh Philosophical Society when it received its royal warrant, he was appointed as the first general secretary to the Royal Society of Edinburgh (1783–98). Robison invented the siren and also worked with James Watt on an early steam car. Following the French Revolution, Robison became disenchanted with elements of the Enlightenment. He authored ''Proofs of a Conspiracy'' in 1797—a polemic accusing Freemasonry of being infiltrated by Weishaupt's Order of the Illuminati. His son was the inventor Sir John Robison (1778–1843). Biography The son of John Robison, a Glasgow merchant, he was born in Boghall, Baldernock, Stirlingshire (now East Dunbartonshire) and attended Glasgow Grammar School and the University of Glasgow (MA 1756). After a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tachometer
A tachometer (revolution-counter, tach, rev-counter, RPM gauge) is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays the revolutions per minute (RPM) on a calibrated analogue dial, but digital displays are increasingly common. The word comes from Greek ''τάχος'' (''táchos'' "speed") and ''μέτρον'' (''métron'' "measure"). Essentially the words tachometer and speedometer have identical meaning: a device that measures speed. It is by arbitrary convention that in the automotive world one is used for engine revolutions and the other for vehicle speed. In formal engineering nomenclature, more precise terms are used to distinguish the two. History The first tachometer was described by an Donkin in a paper to the Royal Society of Arts in 1810 for which he was awarded the Gold medal of the society. This consisted of a bowl of mercury constructed in such a way that centrifugal force caused the leve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Complete Dictionary Of Scientific Biography
The ''Dictionary of Scientific Biography'' is a scholarly reference work that was published from 1970 through 1980 by publisher Charles Scribner's Sons, with main editor the science historian Charles Gillispie, from Princeton University. It consisted of sixteen volumes. It is supplemented by the ''New Dictionary of Scientific Biography''. Both these publications are included in a later electronic book, called the ''Complete Dictionary of Scientific Biography''. ''Dictionary of Scientific Biography'' The ''Dictionary of Scientific Biography'' is a scholarly English-language reference work consisting of biographies of scientists from antiquity to modern times, but excluding scientists who were alive when the ''Dictionary'' was first published. It includes scientists who worked in the areas of mathematics, physics, chemistry, biology, and earth sciences. The work is notable for being one of the most substantial reference works in the field of history of science, containing extensive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human Hearing
Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is auditory science. Sound may be heard through solid, liquid, or gaseous matter. It is one of the traditional five senses. Partial or total inability to hear is called hearing loss. In humans and other vertebrates, hearing is performed primarily by the auditory system: mechanical waves, known as vibrations, are detected by the ear and transduced into nerve impulses that are perceived by the brain (primarily in the temporal lobe). Like touch, audition requires sensitivity to the movement of molecules in the world outside the organism. Both hearing and touch are types of mechanosensation. Hearing mechanism There are three main components of the human auditory system: the outer ear, the middle ear, and the inner ear. Outer ear The outer ear incl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PSM V03 D018 Savart Apparatus
PSM, an acronym, may refer to: Organizations * Sepaktakraw Association of Malaysia ( ms, Persatuan Sepaktakraw Malaysia; PSM), a national governing body in Malaysia. * Pakistan School Muscat, a Pakistani co-educational institute in Oman * Palestine Solidarity Movement, a student organization in the United States * Panhellenic Socialist Movement, a centre-left party in Greece * Parti Sosialis Malaysia, a socialist political party in Malaysia * PlayStation: The Official Magazine, a magazine originally known as PlayStation Magazine or PSM * Ponce School of Medicine, a post-graduate medical school located in Ponce, Puerto Rico * Power Systems Mfg, a subsidiary of Alstom, specializing in aftermarket gas turbine servicing for power generating industry. * ''Poznańska Spółdzielnia Mieszkaniowa'', a housing cooperative administering most of the Piątkowo district of Poznań, Poland * PSM3, a UK video game magazine specializing in Sony consoles * PSM Makassar, a football club that pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perfect Fourth
A fourth is a musical interval encompassing four staff positions in the music notation of Western culture, and a perfect fourth () is the fourth spanning five semitones (half steps, or half tones). For example, the ascending interval from C to the next F is a perfect fourth, because the note F is the fifth semitone above C, and there are four staff positions between C and F. Diminished and augmented fourths span the same number of staff positions, but consist of a different number of semitones (four and six, respectively). The perfect fourth may be derived from the harmonic series as the interval between the third and fourth harmonics. The term ''perfect'' identifies this interval as belonging to the group of perfect intervals, so called because they are neither major nor minor. A perfect fourth in just intonation corresponds to a pitch ratio of 4:3, or about 498 cents (), while in equal temperament a perfect fourth is equal to five semitones, or 500 cents (see additive synt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perfect Fifth
In music theory, a perfect fifth is the musical interval corresponding to a pair of pitches with a frequency ratio of 3:2, or very nearly so. In classical music from Western culture, a fifth is the interval from the first to the last of five consecutive notes in a diatonic scale. The perfect fifth (often abbreviated P5) spans seven semitones, while the diminished fifth spans six and the augmented fifth spans eight semitones. For example, the interval from C to G is a perfect fifth, as the note G lies seven semitones above C. The perfect fifth may be derived from the harmonic series as the interval between the second and third harmonics. In a diatonic scale, the dominant note is a perfect fifth above the tonic note. The perfect fifth is more consonant, or stable, than any other interval except the unison and the octave. It occurs above the root of all major and minor chords (triads) and their extensions. Until the late 19th century, it was often referred to by one of i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interval (music)
In music theory, an interval is a difference in pitch between two sounds. An interval may be described as horizontal, linear, or melodic if it refers to successively sounding tones, such as two adjacent pitches in a melody, and vertical or harmonic if it pertains to simultaneously sounding tones, such as in a chord. In Western music, intervals are most commonly differences between notes of a diatonic scale. Intervals between successive notes of a scale are also known as scale steps. The smallest of these intervals is a semitone. Intervals smaller than a semitone are called microtones. They can be formed using the notes of various kinds of non-diatonic scales. Some of the very smallest ones are called commas, and describe small discrepancies, observed in some tuning systems, between enharmonically equivalent notes such as C and D. Intervals can be arbitrarily small, and even imperceptible to the human ear. In physical terms, an interval is the ratio between two sonic f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physical Property
A physical property is any property that is measurable, whose value describes a state of a physical system. The changes in the physical properties of a system can be used to describe its changes between momentary states. Physical properties are often referred to as observables. They are not modal properties. A quantifiable physical property is called physical quantity. Physical properties are often characterized as intensive and extensive properties. An intensive property does not depend on the size or extent of the system, nor on the amount of matter in the object, while an extensive property shows an additive relationship. These classifications are in general only valid in cases when smaller subdivisions of the sample do not interact in some physical or chemical process when combined. Properties may also be classified with respect to the directionality of their nature. For example, isotropic properties do not change with the direction of observation, and anisotropic prop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
