Misplaced Pages

#88911

122-431: 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 refer to

244-402: A 2001 study deemed it as Canada's most creative neighbourhood because artists comprise 8% of its labour force. The neighbourhood of Mile End in the northwestern part of the borough has been a very multicultural area of the city, and features two of Montreal's well-known bagel establishments , St-Viateur Bagel and Fairmount Bagel . The McGill Ghetto is in the extreme southwestern portion of

366-478: A daily average ranging from −10.5 to −9 °C (13.1 to 15.8 °F) in January. However, some winter days rise above freezing, allowing for rain on an average of 4 days in January and February each. Usually, snow covering some or all bare ground lasts on average from the first or second week of December until the last week of March. While the air temperature does not fall below −30 °C (−22 °F) every year,

488-751: A garrison of 390 men 40 miles upriver in a garrison at Les Cèdres, Quebec , to defend Montreal against the British army. In the Battle of the Cedars , Bedel's lieutenant Isaac Butterfield surrendered to George Forster. Forster advanced to Fort Senneville on May 23. By May 24, Arnold was entrenched in Montreal's borough of Lachine . Forster initially approached Lachine, then withdrew to Quinze-Chênes . Arnold's forces then abandoned Lachine to chase Forster. The Americans burned Senneville on May 26. After Arnold crossed

610-411: A hydrophone/transducer receives a specific interrogation signal it responds by transmitting a specific reply signal. To measure distance, one transducer/projector transmits an interrogation signal and measures the time between this transmission and the receipt of the other transducer/hydrophone reply. The time difference, scaled by the speed of sound through water and divided by two, is the distance between

732-459: A mission on his new seigneury. The colonists left France in 1641 for Quebec and arrived on the island the following year. On May 17, 1642, Ville-Marie was founded on the southern shore of Montreal island, with Maisonneuve as its first governor. The settlement included a chapel and a hospital, under the command of Jeanne Mance . By 1643, Ville-Marie had come under Iroquois raids. In 1652, Maisonneuve returned to France to raise 100 volunteers to bolster

854-500: A narrow arc, although the beam may be rotated, relatively slowly, by mechanical scanning. Particularly when single frequency transmissions are used, the Doppler effect can be used to measure the radial speed of a target. The difference in frequency between the transmitted and received signal is measured and converted into a velocity. Since Doppler shifts can be introduced by either receiver or target motion, allowance has to be made for

976-619: A new settlement at their former hunting grounds north of the Ottawa River. This became Kanesatake . In 1745, several Mohawk families moved upriver to create another settlement, known as Akwesasne . All three are now Mohawk reserves in Canada. The Canadian territory was ruled as a French colony until 1760, when Montreal fell to a British offensive during the Seven Years' War . The colony then surrendered to Great Britain. Ville-Marie

1098-561: A passive ceiling or wall treatment applied to the insides of concert auditoria, such as the Royal Albert Hall . Stansfield, D. (1991). Underwater Electroacoustic Transducers . Peninsula Publishing. 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

1220-487: A pulse to reception is measured and converted into a range using the known speed of sound. To measure the bearing , several hydrophones are used, and the set measures the relative arrival time to each, or with an array of hydrophones, by measuring the relative amplitude in beams formed through a process called beamforming . Use of an array reduces the spatial response so that to provide wide cover multibeam systems are used. The target signal (if present) together with noise

1342-520: A steel tube, vacuum-filled with castor oil , and sealed. The tubes then were mounted in parallel arrays. The standard US Navy scanning sonar at the end of World War II operated at 18 kHz, using an array of ADP crystals. Desired longer range, however, required use of lower frequencies. The required dimensions were too big for ADP crystals, so in the early 1950s magnetostrictive and barium titanate piezoelectric systems were developed, but these had problems achieving uniform impedance characteristics, and

SECTION 10

#1732780817089

1464-525: A system later tested in Boston Harbor, and finally in 1914 from the U.S. Revenue Cutter Miami on the Grand Banks off Newfoundland . In that test, Fessenden demonstrated depth sounding, underwater communications ( Morse code ) and echo ranging (detecting an iceberg at a 2-mile (3.2 km) range). The " Fessenden oscillator ", operated at about 500 Hz frequency, was unable to determine

1586-582: A target ahead of the attacker and still in ASDIC contact. These allowed a single escort to make better aimed attacks on submarines. Developments during the war resulted in British ASDIC sets that used several different shapes of beam, continuously covering blind spots. Later, acoustic torpedoes were used. Early in World War II (September 1940), British ASDIC technology was transferred for free to

1708-413: Is bistatic operation . When more transmitters (or more receivers) are used, again spatially separated, it is multistatic operation . Most sonars are used monostatically with the same array often being used for transmission and reception. Active sonobuoy fields may be operated multistatically. Active sonar creates a pulse of sound, often called a "ping", and then listens for reflections ( echo ) of

1830-419: Is around 1,000 mm (39 in), including an average of about 210 cm (83 in) of snowfall, which occurs from November through March. Thunderstorms are common from late spring through summer to early fall; additionally, tropical storms or their remnants can cause heavy rains and gales. Montreal averages 2,050 hours of sunshine annually, with summer being the sunniest season, though slightly wetter than

1952-465: Is believed to be due to outmigration, epidemics of European diseases, or intertribal wars. In 1611, Champlain established a fur trading post on the Island of Montreal on a site initially named La Place Royale . At the confluence of Petite Riviere and St. Lawrence River , it is where present-day Pointe-à-Callière stands. On his 1616 map, Champlain named the island Lille de Villemenon in honour of

2074-519: Is bordered by the city of Laval to the north; Longueuil , Saint-Lambert , Brossard , and other municipalities to the south; Repentigny to the east and the West Island municipalities to the west. The anglophone enclaves of Westmount , Montreal West , Hampstead , Côte Saint-Luc , the Town of Mount Royal and the francophone enclave Montreal East are all surrounded by Montreal. Montreal

2196-498: Is classified as a warm-summer humid continental climate ( Köppen climate classification : Dfb). Summers are warm to hot and humid with a daily maximum average of 26 to 27 °C (79 to 81 °F) in July; temperatures in excess of 30 °C (86 °F) are common. Conversely, cold fronts can bring crisp, drier and windy weather in the early and later parts of summer. Winter brings cold, snowy, windy, and, at times, icy weather, with

2318-453: Is its zero aging characteristics; the crystal keeps its parameters even over prolonged storage. Another application was for acoustic homing torpedoes. Two pairs of directional hydrophones were mounted on the torpedo nose, in the horizontal and vertical plane; the difference signals from the pairs were used to steer the torpedo left-right and up-down. A countermeasure was developed: the targeted submarine discharged an effervescent chemical, and

2440-580: Is one of the most bilingual cities in Quebec and Canada, with 58.5% of the population able to speak both French and English. Historically the commercial capital of Canada, Montreal was surpassed in population and economic strength by Toronto in the 1970s. It remains an important centre of art, culture , literature, film and television, music, commerce, aerospace, transport , finance, pharmaceuticals, technology, design, education , tourism , food, fashion, video game development, and world affairs. Montreal

2562-415: Is the source level , PL is the propagation loss (sometimes referred to as transmission loss ), TS is the target strength , NL is the noise level , AG is the array gain of the receiving array (sometimes approximated by its directivity index) and DT is the detection threshold . In reverberation-limited conditions at initial detection (neglecting array gain): where RL is the reverberation level , and

SECTION 20

#1732780817089

2684-580: Is the location of the headquarters of the International Civil Aviation Organization , and was named a UNESCO City of Design in 2006. In 2017, Montreal was ranked the 12th-most livable city in the world by the Economist Intelligence Unit in its annual Global Liveability Ranking , although its ranking slipped to 40th in the 2021 index, primarily due to stress on the healthcare system from

2806-691: Is the oldest complete building in the city, built between 1669 and 1671. In Point St. Charles , visitors can see the Maison Saint-Gabriel , which can trace its history back to 1698. There are many historic buildings in Old Montreal in their original form: Notre-Dame Basilica, Bonsecours Market , and the 19th‑century headquarters of all major Canadian banks on St. James Street (French: Rue Saint Jacques ). Montreal's earliest buildings are characterized by their uniquely French influence and grey stone construction. A few notable examples of

2928-427: Is then passed through various forms of signal processing , which for simple sonars may be just energy measurement. It is then presented to some form of decision device that calls the output either the required signal or noise. This decision device may be an operator with headphones or a display, or in more sophisticated sonars this function may be carried out by software. Further processes may be carried out to classify

3050-402: Is very low, several orders of magnitude less than the original signal. Even if the reflected signal was of the same power, the following example (using hypothetical values) shows the problem: Suppose a sonar system is capable of emitting a 10,000 W/m signal at 1 m, and detecting a 0.001 W/m  signal. At 100 m the signal will be 1 W/m (due to the inverse-square law ). If

3172-741: The Titanic disaster of 1912. The world's first patent for an underwater echo-ranging device was filed at the British Patent Office by English meteorologist Lewis Fry Richardson a month after the sinking of Titanic , and a German physicist Alexander Behm obtained a patent for an echo sounder in 1913. The Canadian engineer Reginald Fessenden , while working for the Submarine Signal Company in Boston , Massachusetts, built an experimental system beginning in 1912,

3294-640: The Allied forces , was furious over Houde's stand and held him in a prison camp until 1944. That year, the government decided to institute conscription to expand the armed forces and fight the Axis powers . (See Conscription Crisis of 1944 .) Montreal was the official residence of the Luxembourg royal family in exile during World War II. By 1951, Montreal's population had surpassed one million. However, Toronto's growth had begun challenging Montreal's status as

3416-643: The COVID-19 pandemic . It is regularly ranked as one of the ten best cities in the world to be a university student in the QS World University Rankings . In 2018, Montreal was ranked as a global city . Montreal has hosted numerous important international events, including the 1967 International and Universal Exposition , and is the only Canadian city to have hosted the Summer Olympics, having done so in 1976 . The city hosts

3538-767: The Canadian Grand Prix of Formula One ; the Montreal International Jazz Festival , the largest jazz festival in the world; the Just for Laughs festival, the largest comedy festival in the world; and Les Francos de Montréal , the largest French-language music festival in the world. In sports , it is home to multiple professional teams, most notably the Canadiens of the National Hockey League , who have won

3660-731: The Great Lakes to the Atlantic. Montreal is defined by its location between the Saint Lawrence river to its south and the Rivière des Prairies to its north. The city is named after the most prominent geographical feature on the island, a three-head mountain called Mount Royal, topped at 232 m (761 ft) above sea level . Montreal is at the centre of the Montreal Metropolitan Community , and

3782-587: The Iroquois nations of the Haudenosaunee (then based in present-day New York), established the village of Hochelaga at the foot of Mount Royal two centuries before the French arrived. Archeologists have found evidence of their habitation there and at other locations in the valley since at least the 14th century. The French explorer Jacques Cartier visited Hochelaga on October 2, 1535, and estimated

Tonpilz - Misplaced Pages Continue

3904-536: The Montreal Biosphere , and Moshe Safdie 's striking Habitat 67 apartment complex. The Montreal Metro has public artwork by some of the biggest names in Quebec culture . In 2006, Montreal was named a UNESCO City of Design , one of only three design capitals in the world (the others being Berlin and Buenos Aires ). This distinguished title recognizes Montreal's design community. Since 2005,

4026-610: The Ottawa River in pursuit of Forster, Forster's cannons repelled Arnold's forces. Forster negotiated a prisoner exchange with Henry Sherburne and Isaac Butterfield, resulting in a May 27 boating of their deputy Lieutenant Park being returned to the Americans. Arnold and Forster negotiated further and more American prisoners were returned to Arnold at Sainte-Anne-de-Bellevue, Quebec , ("Fort Anne") on May 30 (delayed two days by wind). Arnold eventually withdrew his forces back to

4148-468: The Plains of Abraham , Montreal fell to American forces led by Richard Montgomery on November 13, 1775, after it was abandoned by Guy Carleton . After Arnold withdrew from Quebec City to Pointe-aux-Trembles on November 19, Montgomery's forces left Montreal on December 1 and arrived there on December 3 to plot to attack Quebec City , with Montgomery leaving David Wooster in charge of the city. Montgomery

4270-458: The Royal Navy had five sets for different surface ship classes, and others for submarines, incorporated into a complete anti-submarine system. The effectiveness of early ASDIC was hampered by the use of the depth charge as an anti-submarine weapon. This required an attacking vessel to pass over a submerged contact before dropping charges over the stern, resulting in a loss of ASDIC contact in

4392-557: The Shaughnessy Village / Concordia U area home to thousands of students at Concordia University . The borough also comprises most of Mount Royal Park , Saint Helen's Island , and Notre-Dame Island . The Plateau Mount Royal borough was a working class francophone area. The largest neighbourhood is the Plateau (not to be confused with the whole borough), which was undergoing considerable gentrification as of 2009, and

4514-672: The Stanley Cup a record 24 times. In the Ojibwe language , the land is called Mooniyaang or Moon’yaang which was "the first stopping place" in the Ojibwe migration story as related in the seven fires prophecy . In the Mohawk language , the land is called Tiohtià:ke . This is an abbreviation of Teionihtiohtiá:kon , which loosely translates as "where the group divided/parted ways." French settlers from La Flèche in

4636-551: The hull or become flooded, the 60 Hz sound from the windings can be emitted from the submarine or ship. This can help to identify its nationality, as all European submarines and nearly every other nation's submarine have 50 Hz power systems. Intermittent sound sources (such as a wrench being dropped), called "transients," may also be detectable to passive sonar. Until fairly recently, an experienced, trained operator identified signals, but now computers may do this. Passive sonar systems may have large sonic databases , but

4758-574: The ninth-largest in North America . Founded in 1642 as Ville-Marie , or "City of Mary", it is now named after Mount Royal , the triple-peaked mountain around which the early settlement was built. The city is centred on the Island of Montreal and a few, much smaller, peripheral islands, the largest of which is Île Bizard . The city is 196 km (122 mi) east of the national capital, Ottawa , and 258 km (160 mi) southwest of

4880-652: The prohibition movement in the United States led to Montreal becoming a destination for Americans looking for alcohol . Unemployment remained high in the city and was exacerbated by the Stock Market Crash of 1929 and the Great Depression . During World War II , Mayor Camillien Houde protested against conscription and urged Montrealers to disobey the federal government's registry of all men and women. The federal government, part of

5002-738: The wind chill often makes the temperature feel this low to exposed skin. Spring and fall are pleasantly mild but prone to drastic temperature changes; spring even more so than fall. Late season heat waves as well as " Indian summers " are possible. Early and late season snow storms can occur in November and March, and more rarely in April. Montreal is generally snow free from late April to late October. However, snow can fall in early to mid-October as well as early to mid-May on rare occasions. The lowest temperature in Environment Canada's books

Tonpilz - Misplaced Pages Continue

5124-493: The 1930s American engineers developed their own underwater sound-detection technology, and important discoveries were made, such as the existence of thermoclines and their effects on sound waves. Americans began to use the term SONAR for their systems, coined by Frederick Hunt to be the equivalent of RADAR . In 1917, the US Navy acquired J. Warren Horton 's services for the first time. On leave from Bell Labs , he served

5246-498: The 1970s, compounds of rare earths and iron were discovered with superior magnetomechanic properties, namely the Terfenol-D alloy. This made possible new designs, e.g. a hybrid magnetostrictive-piezoelectric transducer. The most recent of these improved magnetostrictive materials is Galfenol . Other types of transducers include variable-reluctance (or moving-armature, or electromagnetic) transducers, where magnetic force acts on

5368-410: The 1980s and early 1990s, Montreal experienced a slower rate of economic growth than many other major Canadian cities. Montreal was the site of the 1989 École Polytechnique massacre , one of Canada's worst mass shootings , where 25-year-old Marc Lépine shot and killed 14 people, all of them women, and wounded 14 other people before shooting himself at École Polytechnique . Montreal was merged with

5490-494: The 27 surrounding municipalities on the Island of Montreal on January 1, 2002, creating a unified city encompassing the entire island. There was substantial resistance from the suburbs to the merger, with the perception being that it was forced on the mostly English suburbs by the Parti Québécois. As expected, this move proved unpopular and several mergers were later rescinded. Several former municipalities, totalling 13% of

5612-463: The Admiralty archives. By 1918, Britain and France had built prototype active systems. The British tested their ASDIC on HMS  Antrim in 1920 and started production in 1922. The 6th Destroyer Flotilla had ASDIC-equipped vessels in 1923. An anti-submarine school HMS Osprey and a training flotilla of four vessels were established on Portland in 1924. By the outbreak of World War II ,

5734-700: The British Board of Invention and Research , Canadian physicist Robert William Boyle took on the active sound detection project with A. B. Wood , producing a prototype for testing in mid-1917. This work for the Anti-Submarine Division of the British Naval Staff was undertaken in utmost secrecy, and used quartz piezoelectric crystals to produce the world's first practical underwater active sound detection apparatus. To maintain secrecy, no mention of sound experimentation or quartz

5856-702: The English-allied Iroquois attacked Lachine on the Island of Montreal, committing the worst massacre in the history of New France. By the early 18th century, the Sulpician Order was established there. To encourage French settlement, it wanted the Mohawk to move away from the fur trading post at Ville-Marie. It had a mission village, known as Kahnewake , south of the St Lawrence River. The fathers persuaded some Mohawk to make

5978-607: The French physicist Paul Langevin , working with a Russian immigrant electrical engineer Constantin Chilowsky, worked on the development of active sound devices for detecting submarines in 1915. Although piezoelectric and magnetostrictive transducers later superseded the electrostatic transducers they used, this work influenced future designs. Lightweight sound-sensitive plastic film and fibre optics have been used for hydrophones, while Terfenol-D and lead magnesium niobate (PMN) have been developed for projectors. In 1916, under

6100-574: The Loire valley first named their new town, founded in 1642, Ville Marie ("City of Mary"), named for the Virgin Mary . The current form of the name, Montréal , is generally thought to be derived from Mount Royal ( Mont Royal in French), the triple-peaked hill in the heart of the city. There are multiple explanations for how Mont Royal became Montréal . In 16th century French,

6222-540: The New York fort of Ticonderoga by the summer. On June 15, Arnold's messenger approaching Sorel spotted Carleton returning with a fleet of ships and notified him. Arnold's forces abandoned Montreal (attempting to burn it down in the process) prior to the June 17 arrival of Carleton's fleet. The Americans did not return British prisoners in exchange, as previously agreed, due to accusations of abuse, with Congress repudiating

SECTION 50

#1732780817089

6344-509: The United States. Research on ASDIC and underwater sound was expanded in the UK and in the US. Many new types of military sound detection were developed. These included sonobuoys , first developed by the British in 1944 under the codename High Tea , dipping/dunking sonar and mine -detection sonar. This work formed the basis for post-war developments related to countering the nuclear submarine . During

6466-525: The agreement at the protest of George Washington. Arnold blamed Colonel Timothy Bedel for the defeat, removing him and Lieutenant Butterfield from command and sending them to Sorel for court-martial. The retreat of the American army delayed their court martial until August 1, 1776, when they were convicted and cashiered at Ticonderoga. Bedel was given a new commission by Congress in October 1777 after Arnold

6588-415: The area near the boat. When active sonar is used to measure the distance from the transducer to the bottom, it is known as echo sounding . Similar methods may be used looking upward for wave measurement. Active sonar is also used to measure distance through water between two sonar transducers or a combination of a hydrophone (underwater acoustic microphone) and projector (underwater acoustic speaker). When

6710-502: The attack had the advantage that the German acoustic torpedo was not effective against a warship travelling so slowly. A variation of the creeping attack was the "plaster" attack, in which three attacking ships working in a close line abreast were directed over the target by the directing ship. The new weapons to deal with the ASDIC blind spot were "ahead-throwing weapons", such as Hedgehogs and later Squids , which projected warheads at

6832-510: The beam pattern suffered. Barium titanate was then replaced with more stable lead zirconate titanate (PZT), and the frequency was lowered to 5 kHz. The US fleet used this material in the AN/SQS-23 sonar for several decades. The SQS-23 sonar first used magnetostrictive nickel transducers, but these weighed several tons, and nickel was expensive and considered a critical material; piezoelectric transducers were therefore substituted. The sonar

6954-469: The bearing of the iceberg due to the 3-metre wavelength and the small dimension of the transducer's radiating face (less than 1 ⁄ 3 wavelength in diameter). The ten Montreal -built British H-class submarines launched in 1915 were equipped with Fessenden oscillators. During World War I the need to detect submarines prompted more research into the use of sound. The British made early use of underwater listening devices called hydrophones , while

7076-661: The border between French and English Canada, Ottawa was seen as a compromise between Montreal, Toronto, Kingston and Quebec City, which were all vying to become the young nation's official capital. Ottawa retained the status as capital of Canada when the Province of Canada joined with Nova Scotia and New Brunswick to form the Dominion of Canada in 1867. An internment camp was set up at Immigration Hall in Montreal from August 1914 to November 1918. After World War I ,

7198-423: The borough, its name being derived from the fact that it is home to thousands of McGill University students and faculty members. The Southwest borough was home to much of the city's industry during the late 19th and early-to-mid 20th century. The borough included Goose Village and was historically home to the traditionally working-class Irish neighbourhoods of Griffintown and Point Saint Charles as well as

7320-606: The business arena. The October Crisis and the 1976 election of the Parti Québécois , which supported sovereign status for Quebec, resulted in the departure of many businesses and people from the city. In 1976, Montreal hosted the Summer Olympics . While the event brought the city international prestige and attention, the Olympic Stadium built for the event resulted in massive debt for the city. During

7442-444: The characteristics of the outgoing ping. For these reasons, active sonar is not frequently used by military submarines. A very directional, but low-efficiency, type of sonar (used by fisheries, military, and for port security) makes use of a complex nonlinear feature of water known as non-linear sonar, the virtual transducer being known as a parametric array . Project Artemis was an experimental research and development project in

SECTION 60

#1732780817089

7564-631: The city has been home to the International Council of Graphic Design Associations (Icograda) and the International Design Alliance (IDA). The Underground City (officially RÉSO), an important tourist attraction, is an underground network connecting shopping centres, pedestrian thoroughfares, universities, hotels, restaurants, bistros, subway stations and more, in and around downtown with 32 km (20 mi) of tunnels over 12 km (4.6 sq mi) in

7686-582: The city's 20th-century architecture include Saint Joseph's Oratory , completed in 1967, Ernest Cormier 's Art Deco Université de Montréal main building, the landmark Place Ville Marie office tower, and the controversial Olympic Stadium and surrounding structures. Pavilions designed for the 1967 International and Universal Exposition, popularly known as Expo 67 , featured a wide range of architectural designs. Though most pavilions were temporary structures, several have become landmarks, including Buckminster Fuller 's geodesic dome U.S. Pavilion, now

7808-672: The city's earliest still-standing buildings date back to the late 17th and early 18th centuries. Although most are clustered around the Old Montreal area, such as the Sulpician Seminary adjacent to Notre-Dame Basilica that dates back to 1687, and Château Ramezay , which was built in 1705, examples of early colonial architecture are dotted throughout the city. Situated in Lachine, the Le Ber-Le Moyne House

7930-437: The city's history. Montreal annexed 27 other cities, towns and villages beginning with Hochelaga in 1883, with the last prior to 2002 being Pointe-aux-Trembles in 1982. The 21st century has brought with it a revival of the city's economic and cultural landscape. The construction of new residential skyscrapers, two super-hospitals (the Centre hospitalier de l'Université de Montréal and McGill University Health Centre ),

8052-404: The city. As they lacked modern plumbing systems it was impossible to connect all buildings at once and it also acted as a conservation method. However, the population was not finished rising — it rose from 58,000 in 1852 to 267,000 by 1901. Montreal was the capital of the Province of Canada from 1844 to 1849, but lost its status when a Tory mob burnt down the Parliament building to protest

8174-427: The colonial population. If the effort had failed, Montreal was to be abandoned and the survivors re-located downriver to Quebec City . Before these 100 arrived in the fall of 1653, the population of Montreal was barely 50 people. By 1685, Ville-Marie was home to some 600 colonists, most of them living in modest wooden houses. Ville-Marie became a centre for the fur trade and a base for further exploration . In 1689,

8296-414: The creation of the Quartier des Spectacles , reconstruction of the Turcot Interchange , reconfiguration of the Decarie and Dorval interchanges, construction of the new Réseau express métropolitain , gentrification of Griffintown , subway line extensions and the purchase of new subway cars, the complete revitalization and expansion of Trudeau International Airport , the completion of Quebec Autoroute 30 ,

8418-434: The depth charges had been released, the attacking ship left the immediate area at full speed. The directing ship then entered the target area and also released a pattern of depth charges. The low speed of the approach meant the submarine could not predict when depth charges were going to be released. Any evasive action was detected by the directing ship and steering orders to the attacking ship given accordingly. The low speed of

8540-412: The echoes. Since the original signal is much more powerful, it can be detected many times further than twice the range of the sonar (as in the example). Active sonar have two performance limitations: due to noise and reverberation. In general, one or other of these will dominate, so that the two effects can be initially considered separately. In noise-limited conditions at initial detection: where SL

8662-471: The economic capital of Canada. Indeed, the volume of stocks traded at the Toronto Stock Exchange had already surpassed that traded at the Montreal Stock Exchange in the 1940s. The Saint Lawrence Seaway opened in 1959, allowing vessels to bypass Montreal. In time, this development led to the end of the city's economic dominance as businesses moved to other areas. During the 1960s, there was continued growth as Canada's tallest skyscrapers, new expressways and

8784-461: The electro-acoustic transducers are of the Tonpilz type and their design may be optimised to achieve maximum efficiency over the widest bandwidth, in order to optimise performance of the overall system. Occasionally, the acoustic pulse may be created by other means, e.g. chemically using explosives, airguns or plasma sound sources. To measure the distance to an object, the time from transmission of

8906-427: The entire signal is reflected from a 10 m target, it will be at 0.001 W/m when it reaches the emitter, i.e. just detectable. However, the original signal will remain above 0.001 W/m until 3000 m. Any 10 m target between 100 and 3000 m using a similar or better system would be able to detect the pulse, but would not be detected by the emitter. The detectors must be very sensitive to pick up

9028-509: The forms réal and royal were used interchangeably, so Montréal could simply be a variant of Mont Royal . In the second explanation, the name came from an Italian translation. Venetian geographer Giovanni Battista Ramusio used the name Monte Real to designate Mount Royal in his 1556 map of the region. However, the Commission de toponymie du Québec disputes this explanation. Historiographer François de Belleforest

9150-504: The government as a technical expert, first at the experimental station at Nahant, Massachusetts , and later at US Naval Headquarters, in London , England. At Nahant he applied the newly developed vacuum tube , then associated with the formative stages of the field of applied science now known as electronics , to the detection of underwater signals. As a result, the carbon button microphone , which had been used in earlier detection equipment,

9272-476: 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 extremely high ( ultrasonic ). The study of underwater sound is known as underwater acoustics or hydroacoustics . The first recorded use of

9394-505: The largest individual sonar transducers ever. The advantage of metals is their high tensile strength and low input electrical impedance, but they have electrical losses and lower coupling coefficient than PZT, whose tensile strength can be increased by prestressing . Other materials were also tried; nonmetallic ferrites were promising for their low electrical conductivity resulting in low eddy current losses, Metglas offered high coupling coefficient, but they were inferior to PZT overall. In

9516-498: The late 1950s to mid 1960s to examine acoustic propagation and signal processing for a low-frequency active sonar system that might be used for ocean surveillance. A secondary objective was examination of engineering problems of fixed active bottom systems. The receiving array was located on the slope of Plantagnet Bank off Bermuda. The active source array was deployed from the converted World War II tanker USNS  Mission Capistrano . Elements of Artemis were used experimentally after

9638-404: The magnetostrictive unit was much more reliable. High losses to US merchant supply shipping early in World War II led to large scale high priority US research in the field, pursuing both improvements in magnetostrictive transducer parameters and Rochelle salt reliability. Ammonium dihydrogen phosphate (ADP), a superior alternative, was found as a replacement for Rochelle salt; the first application

9760-417: The main experiment was terminated. This is an active sonar device that receives a specific stimulus and immediately (or with a delay) retransmits the received signal or a predetermined one. Transponders can be used to remotely activate or recover subsea equipment. A sonar target is small relative to the sphere , centred around the emitter, on which it is located. Therefore, the power of the reflected signal

9882-593: The mid-1840s, the City of Montreal installed a water system that would pump water from the St. Lawrence and into cisterns . The cisterns would then be transported to the desired location. This was not the first water system of its type in Montreal, as there had been one in private ownership since 1801. In the middle of the 19th century, water distribution was carried out by "fontainiers". The fountainiers would open and close water valves outside of buildings, as directed, all over

10004-403: The moments leading up to attack. The hunter was effectively firing blind, during which time a submarine commander could take evasive action. This situation was remedied with new tactics and new weapons. The tactical improvements developed by Frederic John Walker included the creeping attack. Two anti-submarine ships were needed for this (usually sloops or corvettes). The "directing ship" tracked

10126-493: The most densely populated part of Montreal. The city is composed of 19 large boroughs , subdivided into neighbourhoods. The boroughs are: Côte-des-Neiges–Notre-Dame-de-Grâce , Le Plateau-Mont-Royal ( The Plateau Mount Royal ) , Outremont and Ville-Marie in the centre; Mercier–Hochelaga-Maisonneuve , Rosemont–La Petite-Patrie and Villeray–Saint-Michel–Parc-Extension in the east; Anjou , Montréal-Nord , Rivière-des-Prairies–Pointe-aux-Trembles and Saint-Léonard in

10248-599: The most neighbourhoods is Ville-Marie, which includes downtown, the historic district of Old Montreal, Chinatown , the Gay Village , the Latin Quarter , the gentrified Quartier international and Cité Multimédia as well as the Quartier des spectacles which is under development. Other neighbourhoods of interest in the borough include the affluent Golden Square Mile neighbourhood at the foot of Mount Royal and

10370-406: The northeast; Ahuntsic-Cartierville , L'Île-Bizard–Sainte-Geneviève , Pierrefonds-Roxboro and Saint-Laurent in the northwest; and Lachine , LaSalle , Le Sud-Ouest ( The Southwest ) and Verdun in the south. Many of these boroughs were independent cities that were forced to merge with Montreal in January 2002 following the 2002 municipal reorganization of Montreal . The borough with

10492-494: The ocean or floats on a taut line mooring at a constant depth of perhaps 100 m. They may also be used by submarines , AUVs , and floats such as the Argo float. Passive sonar listens without transmitting. It is often employed in military settings, although it is also used in science applications, e.g. , detecting fish for presence/absence studies in various aquatic environments – see also passive acoustics and passive radar . In

10614-403: The other factors are as before. An upward looking sonar (ULS) is a sonar device pointed upwards looking towards the surface of the sea. It is used for similar purposes as downward looking sonar, but has some unique applications such as measuring sea ice thickness, roughness and concentration, or measuring air entrainment from bubble plumes during rough seas. Often it is moored on the bottom of

10736-546: The others in terms of total precipitation—mostly from thunderstorms. For over a century and a half, Montreal was the industrial and financial centre of Canada. This legacy has left a variety of buildings including factories, elevators , warehouses , mills, and refineries , that today provide an invaluable insight into the city's history, especially in the downtown area and the Old Port area. There are 50 National Historic Sites of Canada , more than any other city. Some of

10858-502: The passage of the Rebellion Losses Bill . Thereafter, the capital rotated between Quebec City and Toronto until in 1857, Queen Victoria herself established Ottawa as the capital due to strategic reasons. The reasons were twofold. First, because it was located more in the interior of the Province of Canada, it was less susceptible to attack from the United States. Second, and perhaps more importantly, because it lay on

10980-402: The population of the island, voted to leave the unified city in separate referendums in June 2004. The demerger took place on January 1, 2006, leaving 15 municipalities on the island, including Montreal. Demerged municipalities remain affiliated with the city through an agglomeration council that collects taxes from them to pay for numerous shared services. The 2002 mergers were not the first in

11102-473: The population of the native people at Hochelaga to be "over a thousand people". Evidence of earlier occupation of the island, such as those uncovered in 1642 during the construction of Fort Ville-Marie, have effectively been removed. In 1603, French explorer Samuel de Champlain reported that the St ;Lawrence Iroquoians and their settlements had disappeared altogether from the St Lawrence valley. This

11224-402: The projectors consisted of two rectangular identical independent units in a cast-iron rectangular body about 16 by 9 inches (410 mm × 230 mm). The exposed area was half the wavelength wide and three wavelengths high. The magnetostrictive cores were made from 4 mm stampings of nickel, and later of an iron-aluminium alloy with aluminium content between 12.7% and 12.9%. The power

11346-405: The provincial capital, Quebec City . As of 2021, the city had a population of 1,762,949, and a metropolitan population of 4,291,732, making it the second-largest metropolitan area in Canada. French is the city's official language. In 2021, 85.7% of the population of the city of Montreal considered themselves fluent in French while 90.2% could speak it in the metropolitan area. Montreal

11468-410: The pulse. This pulse of sound is generally created electronically using a sonar projector consisting of a signal generator, power amplifier and electro-acoustic transducer/array. A transducer is a device that can transmit and receive acoustic signals ("pings"). A beamformer is usually employed to concentrate the acoustic power into a beam, which may be swept to cover the required search angles. Generally,

11590-456: The radial speed of the searching platform. One useful small sonar is similar in appearance to a waterproof flashlight. The head is pointed into the water, a button is pressed, and the device displays the distance to the target. Another variant is a " fishfinder " that shows a small display with shoals of fish. Some civilian sonars (which are not designed for stealth) approach active military sonars in capability, with three-dimensional displays of

11712-543: The reconstruction of the Champlain Bridge and the construction of a new toll bridge to Laval are helping Montreal continue to grow. Montreal is in the southwest of the province of Quebec. The city covers most of the Island of Montreal at the confluence of the Saint Lawrence and Ottawa Rivers. The port of Montreal lies at one end of the Saint Lawrence Seaway, the river gateway that stretches from

11834-544: The sieur de Villemenon, a French dignitary who was seeking the viceroyship of New France. In 1639, Jérôme Le Royer de La Dauversière obtained the Seigneurial title to the Island of Montreal in the name of the Notre Dame Society of Montreal to establish a Roman Catholic mission to evangelize natives. Dauversière hired Paul Chomedey de Maisonneuve , then age 30, to lead a group of colonists to build

11956-471: The sonar operator usually finally classifies the signals manually. A computer system frequently uses these databases to identify classes of ships, actions (i.e. the speed of a ship, or the type of weapon released and the most effective countermeasures to employ), and even particular ships. Montreal Montreal is the largest city in the province of Quebec , the second-largest in Canada , and

12078-669: The subway system known as the Montreal Metro were finished during this time. Montreal also held the World's Fair of 1967, better known as Expo67 . The 1970s ushered in a period of wide-ranging social and political changes, stemming largely from the concerns of the French-speaking majority about the conservation of their culture and language, given the traditional predominance of the English Canadian minority in

12200-408: 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

12322-437: The surfaces of gaps, and moving coil (or electrodynamic) transducers, similar to conventional speakers; the latter are used in underwater sound calibration, due to their very low resonance frequencies and flat broadband characteristics above them. Active sonar uses a sound transmitter (or projector) and a receiver. When the two are in the same place it is monostatic operation . When the transmitter and receiver are separated it

12444-600: The target and localise it, as well as measuring its velocity. The pulse may be at constant frequency or a chirp of changing frequency (to allow pulse compression on reception). Simple sonars generally use the former with a filter wide enough to cover possible Doppler changes due to target movement, while more complex ones generally include the latter technique. Since digital processing became available pulse compression has usually been implemented using digital correlation techniques. Military sonars often have multiple beams to provide all-round cover while simple ones only cover

12566-405: The target submarine on ASDIC from a position about 1500 to 2000 yards behind the submarine. The second ship, with her ASDIC turned off and running at 5 knots, started an attack from a position between the directing ship and the target. This attack was controlled by radio telephone from the directing ship, based on their ASDIC and the range (by rangefinder) and bearing of the attacking ship. As soon as

12688-556: The technique was in 1490 by Leonardo da Vinci , who used a tube inserted into the water to detect vessels by ear. It was developed during World War I to counter the growing threat of submarine warfare , with an operational passive sonar system in use by 1918. Modern active sonar systems use an acoustic transducer to generate a sound wave which is reflected from target objects. Although some animals ( dolphins , bats , some shrews , and others) have used sound for communication and object detection for millions of years, use by humans in

12810-458: The torpedo went after the noisier fizzy decoy. The counter-countermeasure was a torpedo with active sonar – a transducer was added to the torpedo nose, and the microphones were listening for its reflected periodic tone bursts. The transducers comprised identical rectangular crystal plates arranged to diamond-shaped areas in staggered rows. Passive sonar arrays for submarines were developed from ADP crystals. Several crystal assemblies were arranged in

12932-409: The two platforms. This technique, when used with multiple transducers/hydrophones/projectors, can calculate the relative positions of static and moving objects in water. In combat situations, an active pulse can be detected by an enemy and will reveal a submarine's position at twice the maximum distance that the submarine can itself detect a contact and give clues as to the submarine's identity based on

13054-481: The very broadest usage, this term can encompass virtually any analytical technique involving remotely generated sound, though it is usually restricted to techniques applied in an aquatic environment. Passive sonar has a wide variety of techniques for identifying the source of a detected sound. For example, U.S. vessels usually operate 60 Hertz (Hz) alternating current power systems. If transformers or generators are mounted without proper vibration insulation from

13176-436: The water was initially recorded by Leonardo da Vinci in 1490: a tube inserted into the water was said to be used to detect vessels by placing an ear to the tube. In the late 19th century, an underwater bell was used as an ancillary to lighthouses or lightships to provide warning of hazards. The use of sound to "echo-locate" underwater in the same way as bats use sound for aerial navigation seems to have been prompted by

13298-465: Was a large array of 432 individual transducers. At first, the transducers were unreliable, showing mechanical and electrical failures and deteriorating soon after installation; they were also produced by several vendors, had different designs, and their characteristics were different enough to impair the array's performance. The policy to allow repair of individual transducers was then sacrificed, and "expendable modular design", sealed non-repairable modules,

13420-559: Was a replacement of the 24 kHz Rochelle-salt transducers. Within nine months, Rochelle salt was obsolete. The ADP manufacturing facility grew from few dozen personnel in early 1940 to several thousands in 1942. One of the earliest application of ADP crystals were hydrophones for acoustic mines ; the crystals were specified for low-frequency cutoff at 5 Hz, withstanding mechanical shock for deployment from aircraft from 3,000 m (10,000 ft), and ability to survive neighbouring mine explosions. One of key features of ADP reliability

13542-666: Was assigned to defend Rhode Island in July 1777 . Montreal was incorporated as a city in 1832. The opening of the Lachine Canal permitted ships to bypass the unnavigable Lachine Rapids , while the construction of the Victoria Bridge established Montreal as a major railway hub. The leaders of Montreal's business community had started to build their homes in the Golden Square Mile from about 1850. By 1860, it

13664-545: Was being loaded on the cable-laying vessel, World War I ended and Horton returned home. During World War II, he continued to develop sonar systems that could detect submarines, mines, and torpedoes. He published Fundamentals of Sonar in 1957 as chief research consultant at the US Navy Underwater Sound Laboratory . He held this position until 1959 when he became technical director, a position he held until mandatory retirement in 1963. There

13786-669: Was chosen instead, eliminating the problem with seals and other extraneous mechanical parts. The Imperial Japanese Navy at the onset of World War II used projectors based on quartz . These were big and heavy, especially if designed for lower frequencies; the one for Type 91 set, operating at 9 kHz, had a diameter of 30 inches (760 mm) and was driven by an oscillator with 5 kW power and 7 kV of output amplitude. The Type 93 projectors consisted of solid sandwiches of quartz, assembled into spherical cast iron bodies. The Type 93 sonars were later replaced with Type 3, which followed German design and used magnetostrictive projectors;

13908-414: Was killed in the failed attack and Arnold, who had taken command, sent Brigadier General Moses Hazen to inform Wooster of the defeat. Wooster left Hazen in command on March 20, 1776, as he left to replace Arnold in leading further attacks on Quebec City. On April 19, Arnold arrived in Montreal to take over command from Hazen, who remained as his second-in-command. Hazen sent Colonel Timothy Bedel to form

14030-426: Was little progress in US sonar from 1915 to 1940. In 1940, US sonars typically consisted of a magnetostrictive transducer and an array of nickel tubes connected to a 1-foot-diameter steel plate attached back-to-back to a Rochelle salt crystal in a spherical housing. This assembly penetrated the ship hull and was manually rotated to the desired angle. The piezoelectric Rochelle salt crystal had better parameters, but

14152-609: Was made – the word used to describe the early work ("supersonics") was changed to "ASD"ics, and the quartz material to "ASD"ivite: "ASD" for "Anti-Submarine Division", hence the British acronym ASDIC . In 1939, in response to a question from the Oxford English Dictionary , the Admiralty made up the story that it stood for "Allied Submarine Detection Investigation Committee", and this is still widely believed, though no committee bearing this name has been found in

14274-577: Was provided from a 2 kW at 3.8 kV, with polarization from a 20 V, 8 A DC source. The passive hydrophones of the Imperial Japanese Navy were based on moving-coil design, Rochelle salt piezo transducers, and carbon microphones . Magnetostrictive transducers were pursued after World War II as an alternative to piezoelectric ones. Nickel scroll-wound ring transducers were used for high-power low-frequency operations, with size up to 13 feet (4.0 m) in diameter, probably

14396-512: Was replaced by the precursor of the modern hydrophone . Also during this period, he experimented with methods for towing detection. This was due to the increased sensitivity of his device. The principles are still used in modern towed sonar systems. To meet the defense needs of Great Britain, he was sent to England to install in the Irish Sea bottom-mounted hydrophones connected to a shore listening post by submarine cable. While this equipment

14518-446: Was the first to use the form Montréal with reference to the entire region in 1575. Archaeological evidence in the region indicates that First Nations native people occupied the island of Montreal as early as 4,000 years ago. By the year AD 1000, they had started to cultivate maize . Within a few hundred years, they had built fortified villages. The Saint Lawrence Iroquoians , an ethnically and culturally distinct group from

14640-490: Was the largest municipality in British North America and the undisputed economic and cultural centre of Canada. In the 19th century, maintaining Montreal's drinking water became increasingly difficult with the rapid increase in population. A majority of the drinking water was still coming from the city's harbour, which was busy and heavily trafficked, leading to the deterioration of the water within. In

14762-636: Was the name for the settlement that appeared in all official documents until 1705, when Montreal appeared for the first time, although people referred to the "Island of Montreal" long before then. As part of the American Revolution , the invasion of Quebec resulted after Benedict Arnold captured Fort Ticonderoga in present-day upstate New York in May 1775 as a launching point to Arnold's invasion of Quebec in September . While Arnold approached

14884-414: Was −37.8 °C (−36 °F) on January 15, 1957, and the highest temperature was 37.6 °C (99.7 °F) on August 1, 1975, both at Dorval International Airport . Before modern weather record keeping (which dates back to 1871 for McGill), a minimum temperature almost 5 degrees lower was recorded at 7 a.m. on January 10, 1859, where it registered at −42 °C (−44 °F). Annual precipitation

#88911