A highway is any public or private road or other public way on land. It is used for major roads, but includes other public roads and public tracks: It is not an equivalent term to controlled-access highway, or a translation for autobahn, etc. According to Merriam Webster, the use of the term predates 12th century. According to Etymonline, "high" is in the sense of "main". In North American and Australian English, major roads such as controlled-access highways or arterial roads are state highways. Other roads may be designated "county highways" in the Ontario; these classifications refer to the level of government. In British English, "highway" is a legal term. Everyday use implies roads, while the legal use covers any route or path with a public right of access, including footpaths etc; the term has led to several related derived terms, including highway system, highway code, highway patrol and highwayman. The term highway exists in distinction to "waterway". Major highways are named and numbered by the governments that develop and maintain them.
Australia's Highway 1 is the longest national highway in the world at over 14,500 km or 9,000 mi and runs the entire way around the continent. China has the world's largest network of highways followed by the United States of America; some highways, like the European routes, span multiple countries. Some major highway routes include ferry services, such as U. S. Route 10. Traditionally highways were used on horses, they accommodated carriages and motor cars, facilitated by advancements in road construction. In the 1920s and 1930s, many nations began investing in progressively more modern highway systems to spur commerce and bolster national defense. Major modern highways that connect cities in populous developed and developing countries incorporate features intended to enhance the road's capacity and safety to various degrees; such features include a reduction in the number of locations for user access, the use of dual carriageways with two or more lanes on each carriageway, grade-separated junctions with other roads and modes of transport.
These features are present on highways built as motorways. The general legal definition deals with right of use not the form of construction. A highway is defined in English common law by a number of similarly-worded definitions such as "a way over which all members of the public have the right to pass and repass without hindrance" accompanied by "at all times". A highway might be open to all forms of lawful land traffic or limited to specific types of traffic or combinations of types of traffic. A highway can share ground with a private right of way for which full use is not available to the general public as will be the case with farm roads which the owner may use for any purpose but for which the general public only has a right of use on foot or horseback; the status of highway on most older roads has been gained by established public use while newer roads are dedicated as highways from the time they are adopted. In England and Wales, a public highway is known as "The Queen's Highway"; the core definition of a highway is modified in various legislation for a number of purposes but only for the specific matters dealt with in each such piece of legislation.
This is in the case of bridges and other structures whose ownership, mode of use or availability would otherwise exclude them from the general definition of a highway, examples in recent years are toll bridges and tunnels which have the definition of highway imposed upon them to allow application of most traffic laws to those using them but without causing all of the general obligations or rights of use otherwise applicable to a highway. Scots law is similar to English law with regard to highways but with differing terminology and legislation. What is defined in England as a highway will in Scotland be what is defined by s.151 Roads Act 1984 as a road, that is:- "any way over which there is a public right of passage and includes the road’s verge, any bridge over which, or tunnel through which, the road passes. In American law, the word "highway" is sometimes used to denote any public way used for travel, whether a "road and parkway". Highways have a route number designated by t
A muffler is a device for reducing the noise emitted by the exhaust of an internal combustion engine. The US Patent for an "Exhaust muffler for engines" was awarded to Milton O. Reeves and Marshall T. Reeves of Columbus, Indiana of the Reeves Pulley Company on 11 May 1897. US Patent Office application № 582485 states that they "have invented certain new and useful Improvements in Exhaust-Mufflers for engines". Mufflers are installed within the exhaust system of most internal combustion engines; the muffler is engineered as an acoustic device to reduce the loudness of the sound pressure created by the engine by acoustic quieting. The noise of the burning-hot exhaust gas exiting the engine at high velocity is abated by a series of passages and chambers lined with roving fiberglass insulation and/or resonating chambers harmonically tuned to cause destructive interference, wherein opposite sound waves cancel each other out. An unavoidable side effect of this noise reduction is restriction of the exhaust gas flow, which creates back pressure, which can decrease engine efficiency.
This is because the engine exhaust must share the same complex exit pathway built inside the muffler as the sound pressure that the muffler is designed to mitigate. Some aftermarket mufflers claim to increase engine output and/or reduce fuel consumption by dint of reduced back pressure; this entails less noise reduction. The legality of altering a motor vehicle's original equipment exhaust. Aftermarket mufflers alter the way a vehicle performs, due to back pressure reduction. Howstuffworks: "How Mufflers Work"
Geometry is a branch of mathematics concerned with questions of shape, relative position of figures, the properties of space. A mathematician who works in the field of geometry is called a geometer. Geometry arose independently in a number of early cultures as a practical way for dealing with lengths and volumes. Geometry began to see elements of formal mathematical science emerging in the West as early as the 6th century BC. By the 3rd century BC, geometry was put into an axiomatic form by Euclid, whose treatment, Euclid's Elements, set a standard for many centuries to follow. Geometry arose independently in India, with texts providing rules for geometric constructions appearing as early as the 3rd century BC. Islamic scientists expanded on them during the Middle Ages. By the early 17th century, geometry had been put on a solid analytic footing by mathematicians such as René Descartes and Pierre de Fermat. Since and into modern times, geometry has expanded into non-Euclidean geometry and manifolds, describing spaces that lie beyond the normal range of human experience.
While geometry has evolved throughout the years, there are some general concepts that are more or less fundamental to geometry. These include the concepts of points, planes, surfaces and curves, as well as the more advanced notions of manifolds and topology or metric. Geometry has applications to many fields, including art, physics, as well as to other branches of mathematics. Contemporary geometry has many subfields: Euclidean geometry is geometry in its classical sense; the mandatory educational curriculum of the majority of nations includes the study of points, planes, triangles, similarity, solid figures and analytic geometry. Euclidean geometry has applications in computer science and various branches of modern mathematics. Differential geometry uses techniques of linear algebra to study problems in geometry, it has applications in physics, including in general relativity. Topology is the field concerned with the properties of geometric objects that are unchanged by continuous mappings. In practice, this means dealing with large-scale properties of spaces, such as connectedness and compactness.
Convex geometry investigates convex shapes in the Euclidean space and its more abstract analogues using techniques of real analysis. It has close connections to convex analysis and functional analysis and important applications in number theory. Algebraic geometry studies geometry through the use of multivariate polynomials and other algebraic techniques, it has applications including cryptography and string theory. Discrete geometry is concerned with questions of relative position of simple geometric objects, such as points and circles, it shares many principles with combinatorics. Computational geometry deals with algorithms and their implementations for manipulating geometrical objects. Although being a young area of geometry, it has many applications in computer vision, image processing, computer-aided design, medical imaging, etc; the earliest recorded beginnings of geometry can be traced to ancient Mesopotamia and Egypt in the 2nd millennium BC. Early geometry was a collection of empirically discovered principles concerning lengths, angles and volumes, which were developed to meet some practical need in surveying, construction and various crafts.
The earliest known texts on geometry are the Egyptian Rhind Papyrus and Moscow Papyrus, the Babylonian clay tablets such as Plimpton 322. For example, the Moscow Papyrus gives a formula for calculating the volume of a truncated pyramid, or frustum. Clay tablets demonstrate that Babylonian astronomers implemented trapezoid procedures for computing Jupiter's position and motion within time-velocity space; these geometric procedures anticipated the Oxford Calculators, including the mean speed theorem, by 14 centuries. South of Egypt the ancient Nubians established a system of geometry including early versions of sun clocks. In the 7th century BC, the Greek mathematician Thales of Miletus used geometry to solve problems such as calculating the height of pyramids and the distance of ships from the shore, he is credited with the first use of deductive reasoning applied to geometry, by deriving four corollaries to Thales' Theorem. Pythagoras established the Pythagorean School, credited with the first proof of the Pythagorean theorem, though the statement of the theorem has a long history.
Eudoxus developed the method of exhaustion, which allowed the calculation of areas and volumes of curvilinear figures, as well as a theory of ratios that avoided the problem of incommensurable magnitudes, which enabled subsequent geometers to make significant advances. Around 300 BC, geometry was revolutionized by Euclid, whose Elements considered the most successful and influential textbook of all time, introduced mathematical rigor through the axiomatic method and is the earliest example of the format still used in mathematics today, that of definition, axiom and proof. Although most of the contents of the Elements were known, Euclid arranged them into a single, coherent logical framework; the Elements was known to all educated people in the West until the middle of the 20th century and its contents are still taught in geometry classes today. Archimedes of Syracuse used the method of exhaustion to calculate the area under the arc of a parabola with the summation of an infinite series, gave remarkably accurate approximations of Pi.
He studied the sp
California is a state in the Pacific Region of the United States. With 39.6 million residents, California is the most populous U. S. the third-largest by area. The state capital is Sacramento; the Greater Los Angeles Area and the San Francisco Bay Area are the nation's second and fifth most populous urban regions, with 18.7 million and 9.7 million residents respectively. Los Angeles is California's most populous city, the country's second most populous, after New York City. California has the nation's most populous county, Los Angeles County, its largest county by area, San Bernardino County; the City and County of San Francisco is both the country's second-most densely populated major city after New York City and the fifth-most densely populated county, behind only four of the five New York City boroughs. California's $3.0 trillion economy is larger than that of any other state, larger than those of Texas and Florida combined, the largest sub-national economy in the world. If it were a country, California would be the 5th largest economy in the world, the 36th most populous as of 2017.
The Greater Los Angeles Area and the San Francisco Bay Area are the nation's second- and third-largest urban economies, after the New York metropolitan area. The San Francisco Bay Area PSA had the nation's highest GDP per capita in 2017 among large PSAs, is home to three of the world's ten largest companies by market capitalization and four of the world's ten richest people. California is considered a global trendsetter in popular culture, innovation and politics, it is considered the origin of the American film industry, the hippie counterculture, fast food, the Internet, the personal computer, among others. The San Francisco Bay Area and the Greater Los Angeles Area are seen as global centers of the technology and entertainment industries, respectively. California has a diverse economy: 58% of the state's economy is centered on finance, real estate services and professional, scientific and technical business services. Although it accounts for only 1.5% of the state's economy, California's agriculture industry has the highest output of any U.
S. state. California is bordered by Oregon to the north and Arizona to the east, the Mexican state of Baja California to the south; the state's diverse geography ranges from the Pacific Coast in the west to the Sierra Nevada mountain range in the east, from the redwood–Douglas fir forests in the northwest to the Mojave Desert in the southeast. The Central Valley, a major agricultural area, dominates the state's center. Although California is well-known for its warm Mediterranean climate, the large size of the state results in climates that vary from moist temperate rainforest in the north to arid desert in the interior, as well as snowy alpine in the mountains. Over time and wildfires have become more pervasive features. What is now California was first settled by various Native Californian tribes before being explored by a number of European expeditions during the 16th and 17th centuries; the Spanish Empire claimed it as part of Alta California in their New Spain colony. The area became a part of Mexico in 1821 following its successful war for independence but was ceded to the United States in 1848 after the Mexican–American War.
The western portion of Alta California was organized and admitted as the 31st state on September 9, 1850. The California Gold Rush starting in 1848 led to dramatic social and demographic changes, with large-scale emigration from the east and abroad with an accompanying economic boom; the word California referred to the Baja California Peninsula of Mexico. The name derived from the mythical island California in the fictional story of Queen Calafia, as recorded in a 1510 work The Adventures of Esplandián by Garci Rodríguez de Montalvo; this work was the fifth in a popular Spanish chivalric romance series that began with Amadis de Gaula. Queen Calafia's kingdom was said to be a remote land rich in gold and pearls, inhabited by beautiful black women who wore gold armor and lived like Amazons, as well as griffins and other strange beasts. In the fictional paradise, the ruler Queen Calafia fought alongside Muslims and her name may have been chosen to echo the title of a Muslim leader, the Caliph. It's possible.
Know ye that at the right hand of the Indies there is an island called California close to that part of the Terrestrial Paradise, inhabited by black women without a single man among them, they lived in the manner of Amazons. They were robust of body with great virtue; the island itself is one of the wildest in the world on account of the craggy rocks. Shortened forms of the state's name include CA, Cal. Calif. and US-CA. Settled by successive waves of arrivals during the last 10,000 years, California was one of the most culturally and linguistically diverse areas in pre-Columbian North America. Various estimates of the native population range from 100,000 to 300,000; the Indigenous peoples of California included more than 70 distinct groups of Native Americans, ranging from large, settled populations living on the coast to groups in the interior. California groups were diverse in their political organization with bands, villages, on the resource-rich coasts, large chiefdoms, such as the Chumash and Salinan.
Trade, intermarriage a
Architectural acoustics is the science and engineering of achieving a good sound within a building and is a branch of acoustical engineering. The first application of modern scientific methods to architectural acoustics was carried out by Wallace Sabine in the Fogg Museum lecture room who applied his new found knowledge to the design of Symphony Hall, Boston. Architectural acoustics can be about achieving good speech intelligibility in a theatre, restaurant or railway station, enhancing the quality of music in a concert hall or recording studio, or suppressing noise to make offices and homes more productive and pleasant places to work and live in. Architectural acoustic design is done by acoustic consultants; this science analyzes noise transmission from building exterior envelope to vice versa. The main noise paths are roofs, walls, windows and penetrations. Sufficient control ensures space functionality and is required based on building use and local municipal codes. An example would be providing a suitable design for a home, to be constructed close to a high volume roadway, or under the flight path of a major airport, or of the airport itself.
The science of limiting and/or controlling noise transmission from one building space to another to ensure space functionality and speech privacy. The typical sound paths are ceilings, room partitions, acoustic ceiling panels, windows, flanking and other penetrations. Technical solutions depend on the source of the noise and the path of acoustic transmission, for example noise by steps or noise by flow vibrations. An example would be providing suitable party wall design in an apartment complex to minimize the mutual disturbance due to noise by residents in adjacent apartments; this is the science of controlling a room's surfaces based on sound absorbing and reflecting properties. Excessive reverberation time, which can be calculated, can lead to poor speech intelligibility. Sound reflections create standing waves that produce natural resonances that can be heard as a pleasant sensation or an annoying one. Reflective surfaces can be angled and coordinated to provide good coverage of sound for a listener in a concert hall or music recital space.
To illustrate this concept consider the difference between a modern large office meeting room or lecture theater and a traditional classroom with all hard surfaces. Interior building surfaces finishes. Ideal acoustical panels are those without a face or finish material that interferes with the acoustical infill or substrate. Fabric covered. Perforated metal shows sound absorbing qualities. Finish material is used to cover over the acoustical substrate. Mineral fiber board, or Micore, is a used acoustical substrate. Finish materials consist of fabric, wood or acoustical tile. Fabric can be wrapped around substrates to create what is referred to as a "pre-fabricated panel" and provides good noise absorption if laid onto a wall. Prefabricated panels are limited to the size of the substrate ranging from 2 by 4 feet to 4 by 10 feet. Fabric retained in a wall-mounted perimeter track system, is referred to as "on-site acoustical wall panels"; this is constructed by framing the perimeter track into shape, infilling the acoustical substrate and stretching and tucking the fabric into the perimeter frame system.
On-site wall panels can be constructed to accommodate door frames, baseboard, or any other intrusion. Large panels can be created on ceilings with this method. Wood finishes can consist of punched or routed slots and provide a natural look to the interior space, although acoustical absorption may not be great. There are four ways to solve workplace sound problems -- the ABCDs. A = Absorb B = Block C = Cover-up D = Diffuse Building services noise control is the science of controlling noise produced by: ACMV systems in buildings, termed HVAC in North America Elevators Electrical generators positioned within or attached to a building Any other building service infrastructure component that emits sound. Inadequate control may lead to elevated sound levels within the space which can be annoying and reduce speech intelligibility. Typical improvements are vibration isolation of mechanical equipment, sound traps in ductwork. Sound masking can be created by adjusting HVAC noise to a predetermined level.
Acoustic transmission Noise health effects Noise mitigation Noise Reduction Coefficient Noise regulation Noise and harshness Room acoustics Sound transmission class Wallace Clement Sabine Acoustical Society of America American Institute of Architects National Council of Acoustical Consultants Institute of Acoustics Speech Privacy Calculator Optimum sizes for small rooms Concert Hall Acoustics Everything You Always Wanted to Know About Concert Hall Acoustics An on-line version of an exhibition on concert hall acoustics shown at the South Bank Centre, London
Noise control or noise mitigation is a set of strategies to reduce noise pollution or to reduce the impact of that noise, whether outdoors or indoors. The main areas of noise mitigation or abatement are: transportation noise control, architectural design, urban planning through zoning codes, occupational noise control. Roadway noise and aircraft noise are the most pervasive sources of environmental noise. Social activities may generate noise levels that affect the health of populations residing in or occupying areas, both indoor and outdoor, near entertainment venues that feature amplified sounds and music that present significant challenges for effective noise mitigation strategies. Multiple techniques have been developed to address interior sound levels, many of which are encouraged by local building codes. In the best case of project designs, planners are encouraged to work with design engineers to examine trade-offs of roadway design and architectural design; these techniques include design of exterior walls, party walls, floor and ceiling assemblies.
Many of these techniques rely upon material science applications of constructing sound baffles or using sound-absorbing liners for interior spaces. Industrial noise control is a subset of interior architectural control of noise, with emphasis on specific methods of sound isolation from industrial machinery and for protection of workers at their task stations. Sound masking is the active addition of noise to reduce the annoyance of certain sounds. Organizations each have their own standards, recommendations/guidelines, directives for what levels of noise workers are permitted to be around before noise controls must be put into place. OSHA's requirements state that when workers are exposed to noise levels above 90 A-weighted decibels in 8-hour time-weighted averages, administrative controls and/or new engineering controls must be implemented in the workplace. OSHA requires that impulse noises and impact noises must be controlled to prevent these noises reaching past 140 dB peak sound pressure levels.
MSHA requires that administrative and/or engineering controls must be implemented in the workplace when miners are exposed to levels above 90 dBA TWA. If noise levels exceed 115 dBA, miners are required to wear hearing protection. MSHA, requires that noise levels be reduced below 115 dB TWA. Measuring noise levels for noise control decision making must integrate all noises from 90dBA to 140 dBA; the FRA recommends that worker exposure to noise should be reduced when their noise exposure exceeds 90 dBA for an 8-hour TWA. Noise measurements must integrate all noises, including intermittent, continuous and impulse noises between 80 dBA to 140 dBA; the DoD suggests that noise levels be controlled through engineering controls. The DoD requires that all steady-state noises be reduced to levels below 85 dBA and that impulse noises be reduced below 140 dB peak SPL. Time Weighted Average exposures are not considered for the DoD's requirements; the European Parliament and Council directive require noise levels to be reduced or eliminated using administrative and engineering controls.
This directive requires lower exposure action levels of 80 dBA for 8 hours with 135 dB peak SPL, along with upper exposure action levels of 85 dBA for 8 hours with 137 peak dBSPL. Exposure limits are 87 dBA for 8 hours with peak levels of 140 peak dBSPL. An effective model for noise control is the source and receiver model by Bolt and Ingard. Hazardous noise can be controlled by reducing the noise output at its source, minimizing the noise as it travels along a path to the listener, providing equipment to the listener or receiver to attenuate the noise. A variety of measures aim to reduce hazardous noise at its source. Programs such as Buy Quiet and the National Institute for Occupational Safety and Health Prevention through design promote research and design of quiet equipment and renovation and replacement of older hazardous equipment with modern technologies. Physical materials, such as foam, absorb sound and walls to provide a sound barrier that modifies existing systems that decrease hazardous noise at the source.
The principle of noise reduction through pathway modifications applies to the alteration of direct and indirect pathways for noise. Noise that travels across reflective surfaces, such as smooth floors, can be hazardous. Pathway alterations include sound dampening enclosures for loud equipment and isolation chambers from which workers can remotely control equipment while removed from noise; these methods prevent sound from traveling along a path to other listener. In the industrial or commercial setting, workers must comply with the appropriate Hearing conservation program. Administrative controls, such as the restriction of personnel in noisy areas, prevents unnecessary noise exposure. Personal protective equipment such as foam ear plugs or ear muffs to attenuate sound provide a last line of defense for the listener. Sound insulation: prevent the transmission of noise by the introduction of a mass barrier. Common materials have high-density properties such as brick, thick glass, metal etc. Sound absorption: a porous material which acts as a ‘noise sponge’ by converting the sound energy into heat within the material.
Common sound absorption materials include decoupled lead-based tiles, open cell foams and fiberglass Vibration damping: applicable for large vibrating surfaces. The damping mechanism works by extracting the vibration energy from the thin sheet and dissipating it as heat. A co
A loudspeaker enclosure or loudspeaker cabinet is an enclosure in which speaker drivers and associated electronic hardware, such as crossover circuits and, in some cases, power amplifiers, are mounted. Enclosures may range in design from simple, homemade DIY rectangular particleboard boxes to complex, expensive computer-designed hi-fi cabinets that incorporate composite materials, internal baffles, bass reflex ports and acoustic insulation. Loudspeaker enclosures range in size from small "bookshelf" speaker cabinets with 4" woofers and small tweeters designed for listening to music with a hi-fi system in a private home to huge, heavy subwoofer enclosures with multiple 18" or 21" speakers in huge enclosures which are designed for use in stadium concert sound reinforcement systems for rock music concerts; the primary role of the enclosure is to prevent sound waves generated by the rearward-facing surface of the diaphragm of an open speaker driver interacting with sound waves generated at the front of the speaker driver.
Because the forward- and rearward-generated sounds are out of phase with each other, any interaction between the two in the listening space creates a distortion of the original signal as it was intended to be reproduced. As such, a loudspeaker cannot be used without installing it in a cabinet of some type, or mounting it into a wall or ceiling. Additionally, because the sound waves would travel different paths through the listening space, the sound waves in an unmounted speaker would arrive at the listener's position at different times, introducing echo and reverberation effects not part of the original sound; the enclosure plays a role in managing vibration induced by the driver frame and moving airmass within the enclosure, as well as heat generated by driver voice coils and amplifiers. Sometimes considered part of the enclosure, the base, may include specially designed "feet" to decouple the speaker from the floor. Enclosures designed for use in PA systems, sound reinforcement systems and for use by electric musical instrument players.
Speaker enclosures designed for use in a home or recording studio do not have handles or corner protectors, although they do still have a cloth or mesh cover to protect the woofer and tweeter. These speaker grilles are a metallic or cloth mesh that are used to protect the speaker by forming a protective cover over the speaker's cone while allowing sound to pass through undistorted. Speaker enclosures are used in homes in stereo systems, home cinema systems, boom boxes and many other audio appliances. Small speaker enclosures are used in car stereo systems. Speaker cabinets are key components of a number of commercial applications, including sound reinforcement systems, movie theatre sound systems and recording studios. Electric musical instruments invented in the 20th century, such as the electric guitar, electric bass and synthesizer, among others, are amplified using instrument amplifiers and speaker cabinets. Early on, radio loudspeakers consisted of horns sold separately from the radio itself, so they were not housed in an enclosure.
When paper cone loudspeaker drivers were introduced in the mid 1920s, radio cabinets began to be made larger to enclose both the electronics and the loudspeaker. These cabinets were made for the sake of appearance, with the loudspeaker mounted behind a round hole in the cabinet, it was observed. Since the rear of the loudspeaker radiates sound out of phase from the front, there can be constructive and destructive interference for loudspeakers without enclosures, below frequencies related to the baffle dimensions in open-baffled loudspeakers; this results in a loss of comb filtering. Before the 1950s many manufacturers did not enclose their loudspeaker cabinets; this was done for several reasons, not least because electronics could be placed inside and cooled by convection in the open enclosure. Most of the enclosure types discussed in this article were invented either to wall off the out of phase sound from one side of the driver, or to modify it so that it could be used to enhance the sound produced from the other side.
However, a few designs have ventured in a different direction, attempting to incorporate the natural acoustic properties of the cabinet material rather than deaden it, shape the cabinet so that the rear can remain open and still provide good bass response with limited comb filtering. In some respects, the ideal mounting for a low-frequency loudspeaker driver would be a rigid flat panel of infinite size with infinite space behind it; this would prevent the rear sound waves from interfering with the sound waves from the front. An "open baffle" loudspeaker is an approximation of this, since the driver is mounted on a panel, with dimensions comparable to the lowest wavelength to be reproduced. In either case, the driver would need a stiff suspension to provide the restoring force which might have been provided at low frequencies by a smaller sealed or ported enclosure, so few drivers are suitable for this kind of mount