Factory instruments for physical research
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- Paving a Way to the Digital Plant
- Air Monitoring, Measuring, and Emissions Research
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- The science of making musical instruments
- Top Instrument Firms of 2018
- Future Factory: How Technology Is Transforming Manufacturing
- Science and the Stradivarius
- Wireless User Requirements for the Factory Workcell
- Why Some Factories Are More Productive Than Others
Paving a Way to the Digital Plant
Thank you for registering with Physics World If you'd like to change your details at any time, please visit My account. Is there a secret that makes a Stradivarius sound so good, and can modern violins match the wonderful tonal quality of this great Italian instrument, asks Colin Gough.
Is there really a lost secret that sets Stradivarius violins apart from the best instruments made today? After more than a hundred years of vigorous debate, this question remains highly contentious, provoking strongly held but divergent views among players, violin makers and scientists alike. All of the greatest violinists of modern times certainly believe it to be true, and invariably perform on violins by Stradivari or Guarneri in preference to modern instruments.
Violins by the great Italian makers are, of course, beautiful works of art in their own right, and are coveted by collectors as well as players. Particularly outstanding violins have reputedly changed hands for over a million pounds. Do such prices really reflect such large differences in quality?
The violin is the most highly developed and most sophisticated of all stringed instruments. It emerged in Northern Italy in about , in a form that has remained essentially unchanged ever since. The famous Cremonese violin-making families of Amati, Stradivari and Guarneri formed a continuous line of succession that flourished from about to , with skills being handed down from father to son and from master to apprentice.
The popular belief is that their unsurpassed skills, together with the magical Stradivarius secret, were lost by the start of the 19th century. Just as any musician can immediately recognize the difference between Domingo and Pavarotti singing the same operatic aria, so a skilled violinist can distinguish between different qualities in the sound produced by individual Stradivari or Guarneri violins.
The challenge for scientists is to characterize such differences by physical measurements. Indeed, over the last century and a half, many famous physicists have been intrigued by the workings of the violin, with Helmholtz, Savart and Raman all making vital contributions. Prominent among the 19th-century violin restorers was the French maker Vuillaume, whose copy of a Guarnerius violin is shown above left.
Vuillaume worked closely with Felix Savart, best known to physicists for the Biot-Savart law in electromagnetism, to enhance the tone of early instruments. Vuillaume, Savart and others wanted to produce more powerful and brilliant sounding instruments that could stand out in the larger orchestras and concert halls of the day.
Improvements in instrument design were also introduced to support the technical demands of great violin virtuosi like Paganini. To understand the factors that determine the quality of sound produced by particular instruments, we must first recall how the violin works figure 1. Sound is produced by drawing a bow across one or more of the four stretched strings.
The string tensions are adjusted by tuning pegs at one end of the string, so that their fundamental frequencies are about , , and Hz — which correspond to the notes G, D, A and E. However, the strings themselves produce almost no sound. To produce sound, energy from the vibrating string is transferred to the main body of the instrument — the so-called sound box. The main plates of the violin act rather like a loudspeaker cone, and it is the vibrations of these plates that produce most of the sound.
The bridge converts the transverse forces of the strings into the vibrational modes of the sound box. And because the bridge has its own resonant modes, it plays a key role in the overall tone of the instrument. The front plate of the violin is carved from a solid block of fine-grained pine. Maple is usually used for the back plate and pine for the sides. The carving of the f-holes often helps to identify the maker of a valuable instrument: never rely on the label inside the violin to spot a fake instrument as the label will probably have been forged as well.
The f-holes play a number of important acoustic roles. By breaking up the area of the front plate, they affect its vibrational modes at the highest frequencies. More importantly, they boost the sound output at low frequencies.
The resonant frequency is determined by the area of the f-holes and the volume of the instrument. It is the only acoustic resonance of the instrument over which violin makers have almost complete control. The force exerted by the bowed strings causes the bridge to rock about this position, causing the other side of the plate to vibrate with a larger amplitude.
This increases the radiating volume of the violin and produces a much stronger sound. The bass bar and sound post were both made bigger in the 19th century to strengthen the instrument and to increase the sound output. In the 19th century the German physicist Hermann von Helmholtz showed that when a violin string is bowed, it vibrates in a way that is completely different from the sinusoidal standing waves that are familiar to all physicists.
Although the string vibrates back and forth parallel to the bowing direction, Helmholtz showed that other transverse vibrations of the string could also be excited, made up of straight-line sections. The bowing action excites a Helmholtz mode with a single kink separating two straight sections figure 2. When the kink is between the bow and the fingered end of the string, the string moves at the same speed and in the same direction as the bow.
Only a small force is needed to lock the two motions together. But as soon as the kink moves past the bow — on its way to the bridge and back — the string slips past the bow and starts moving in the opposite direction to it. Although the sliding friction is relatively small in the slipping regime, energy is continuously transferred from the strings to the vibrational modes of the instrument at the bridge. Each time the kink reflects back from the bridge and passes underneath the bow, the bow has to replace the lost energy.
It therefore exerts a short impulse on the string so that it moves again at the same velocity as the bow. The Helmholtz wave generates a transverse force T sin q on the bridge, where q is the angle of the string at the bridge. This force increases linearly with time, but its amplitude reverses suddenly each time the kink is reflected at the bridge, producing a sawtooth waveform figure 2d.
The detailed physics of the way a bow excites a string has been extensively studied by Michael McIntyre and Jim Woodhouse at Cambridge University, who have made a number of important theoretical and experimental contributions to violin acoustics in recent years. It is important to recognize that the Helmholtz wave is a free mode of vibration of the string. The player has to apply just the right amount of pressure to excite and maintain the waveform without destroying it.
The lack of such skill is one of the main reasons why the sound produced by a beginner is so excruciating. Conversely, the intensity, quality and subtlety of sound produced by great violinists is mainly due to the fact that they can control the Helmholtz waveform with the bow. The quality of sound produced by any violin therefore depends as much on the bowing skill of the violinist as on the physical properties.
The sawtooth force that is generated on the top of the bridge by a bowed string is the input signal that forces the violin to vibrate and radiate sound — rather like the electrical input to a loudspeaker, albeit with a much more complicated frequency response. The input sawtooth waveform has a rich harmonic content, consisting of numerous Fourier components.
The amplitude of each partial in the radiated sound is determined by the response of the instrument at that particular frequency. This is largely determined by the mechanical resonances of the bridge and by the body of the instrument. These resonances are illustrated schematically in figure 3, where typical responses have been mathematically modelled to simulate their influence on the sound produced. At low frequencies the bridge simply acts as a mechanical lever, since the response is independent of frequency.
However, between 2. This boosts the intensity of any partials in this frequency range, where the ear is most sensitive, and gives greater brightness and carrying power to the sound. Another resonance occurs at about 4. Between these two resonances there is a strong dip in the transfer of force to the body. Thankfully this dip decreases the amplitude of the partials at these frequencies, which the ear associates with an unpleasant shrillness in musical quality.
The sinusoidal force exerted by the bridge on the top plate produces an acoustic output that can be modelled mathematically. The output increases dramatically whenever the exciting frequency coincides with one of the many vibrational modes of the instrument. Indeed, the violin is rather like a loudspeaker with a highly non-uniform frequency response that peaks every time a resonance is excited.
The modelled response is very similar to many recorded examples made on real instruments. In practice, quite small changes in the arching, thickness and mass of the individual plates can result in big changes in the resonant frequencies of the violin, which is why no two instruments ever sound exactly alike.
The multi-resonant response leads to dramatic variations in the amplitudes of individual partials for any note played on the violin. Such factors must have unconsciously guided the radical redesign of the bridge in the 19th century. It is therefore surprising that so few players — or even violin makers — recognize the major importance of the bridge in determining the overall tone quality of an instrument. One of the reasons for the excellent tone of the very best violins is the attention that top players give to the violin set-up — rather like the way in which a car engine is tuned to get the best performance.
Violinists will, for example, carefully adjust the bridge to suit a particular instrument — or even select a different bridge altogether.
The sound quality of many modern violins could undoubtedly be improved by taking just as much care in selecting and adjusting the bridge.
The transfer of energy from the vibrating string to the acoustically radiating structural modes is clearly essential for the instrument to produce any sound. However, this coupling must not be too strong, otherwise the instrument becomes difficult to play and the violinist has to work hard to maintain the Helmholtz wave. Indeed, a complete breakdown can occur when a string resonance coincides with a particularly strongly coupled and lightly damped structural resonance.
However, this only moves the wolf-note to a note that is not played as often, rather than eliminating it entirely. The Helmholtz motion of the string and the wolf-note problem were extensively studied by the Indian physicist Chandrasekhara Raman in the early years of the 20th century.
His results were published in a series of elegant theoretical and experimental papers soon after he founded the Indian Academy of Sciences and before the work on optics that earned him the Nobel Prize for Physics in Indeed, there is just as much variation between the individual notes on a single instrument as there is between the same note played on different instruments. This implies that the perceived tone of a violin must be related to overall design of the instrument, rather than to the frequencies of particular resonances on an instrument.
He measured the acoustic output of 10 Italian violins, 10 fine modern copies and 10 factory-made violins, all of which were excited by an electromagnetic driver on one side of the bridge figure 4. Between and Hz, the factory-made violins were found — surprisingly — to be closer to the Italian instruments than the modern copies.
At frequencies above Hz, however, the factory-made instruments had a rather weak response — in contrast to the over-strong response of the modern violins, which may contribute to a certain shrillness in their quality. In practice it is extremely difficult to distinguish between a particularly fine Stradivarius instrument and an indifferent modern copy on the basis of the measured response alone. The ear is a supreme detection device and the brain is a far more sophisticated analyser of complex sounds than any system yet developed to assess musical quality.
Although such measurements give the frequencies of important acoustic resonances, they tell us nothing about the way a violin actually vibrates.
A powerful technique for investigating such vibrations is called time-averaged interference holography. Bernard Richardson, a physicist at Cardiff University in the UK, has made a number of such studies on the guitar and violin. Some particularly beautiful examples for the guitar are shown in figure 5. Unfortunately, it is not easy to obtain similar high-quality images for the violin because it is smaller, the vibrations of the surface are smaller, and the surfaces of the violin are more curved and less reflective than those of the guitar.
Another powerful approach is modal analysis: a violin is lightly struck with a calibrated hammer at several positions and the transient response at various points is measured with a very light accelerometer. These responses are then analysed by computer to give the resonant frequencies and structural modes of vibration of the whole instrument.
This technique has been used to teach students about violin acoustics at the famous Mittenwald school of violin making in Germany and by Ken Marshall in the US.
Marshall has also shown that the way the violin is held has little effect on its resonant response.
Air Monitoring, Measuring, and Emissions Research
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Pressure to bring more products to market faster while maintaining quality and control has food and beverage manufacturers digitizing many aspects of the process, aiming to connect the farm to the factory—and beyond. In , General Mills introduced a gluten-free version of Cheerios. Although the oats used in the cereal are naturally gluten-free, there are many places in the supply chain and on the production line where the grain can be contaminated by wheat, rye or barley. During the development of a mechanical sorting system to separate the oats from the other grains, it became clear that this new go-to-market strategy could also be the perfect pilot project to test out the technologies and open platforms being developed by the Smart Manufacturing Leadership Coalition SMLC. SMLC is a non-profit organization focusing on the creation of a collaborative business model to lower costs, share precompetitive practices and technologies, and facilitate innovation through value-added processes.
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The science of making musical instruments
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Top Instrument Firms of 2018
How can you take string or a tube and create a device to make music? Here's the science behind the tools of art. Please be aware that the information provided on this page may be out of date, or otherwise inaccurate due to the passage of time. For more detail, see our Archive and Deletion Policy. Interested in the technology of music?
Future Factory: How Technology Is Transforming Manufacturing
Federal government websites often end in. The site is secure. Author s Karl R. Abstract Wireless communication is becoming crucial to advanced manufacturing. Industry 4. The term Industrial Internet of Things IIoT has been used to describe the deployment of interconnected machines, sensors, and actuators within modernized factories.
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Science and the Stradivarius
Musical instrument , any device for producing a musical sound. The principal types of such instruments, classified by the method of producing sound, are percussion , stringed , keyboard , wind , and electronic. Musical instruments are almost universal components of human culture: archaeology has revealed pipes and whistles in the Paleolithic Period and clay drums and shell trumpets in the Neolithic Period. It has been firmly established that the ancient city cultures of Mesopotamia, the Mediterranean, India , East Asia, and the Americas all possessed diverse and well-developed assortments of musical instruments, indicating that a long previous development must have existed.
Wireless User Requirements for the Factory Workcell
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Instrumentation is a collective term for measuring instruments that are used for indicating, measuring and recording physical quantities such as flow, temperature, level, distance, angle, or pressure. The term has its origins in the art and science of scientific instrument-making. Instrumentation can refer to devices as simple as direct-reading thermometers , or as complex as multi-sensor components of industrial control systems. Today, instruments can be found in laboratories, refineries, factories and vehicles, as well as in everyday household use e.
Thank you for registering with Physics World If you'd like to change your details at any time, please visit My account. Is there a secret that makes a Stradivarius sound so good, and can modern violins match the wonderful tonal quality of this great Italian instrument, asks Colin Gough. Is there really a lost secret that sets Stradivarius violins apart from the best instruments made today? After more than a hundred years of vigorous debate, this question remains highly contentious, provoking strongly held but divergent views among players, violin makers and scientists alike. All of the greatest violinists of modern times certainly believe it to be true, and invariably perform on violins by Stradivari or Guarneri in preference to modern instruments. Violins by the great Italian makers are, of course, beautiful works of art in their own right, and are coveted by collectors as well as players.
Why Some Factories Are More Productive Than Others
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