ENGLISH FOR MECHATRONICS

THE UNIVERSITY OF DANANG COLLEGE OF FOREIGN LANGUAG ES DEPARTMENT OF ENGLISH FOR SPECIFIC PURPOSES -   - NGUYỄN THỊ CẨM TÚ, M.A Danang 2010 UNIT INTRODUCTION TO MECHATRONICS AND MEASUREMENT SYSTEMS Warm-up Think of the combination of the two words breakfast and lunch into one word, or motorist and hotel Can you guess the two original words of smog, spork, knork, netizen, wikipedia, Vietlish or in non-standard English, jorts, skorts, jat? Now this time, identify the two original words of mechatronics and say what you guess it is Reading skill SKIMMING FOR GENERAL IDEAS Skimming is one of the useful reading skills to quickly gather the most important information, or 'gist' Run your eyes over the text, noting important information It's not essential to understand each word when skimming By using this skill, you can quickly discover which parts of the text you would like to read in more detail according to your reading purposes EXERCISE A Skim the text below to find which paragraph contains: a General terms used in a system of measurement b Basic equipment in a mechatronic system c Necessity of the combination of mechanical engineering with electronic and electrical engineering d Development of mechanical engineering due to industrial revolution Reading Comprehension Mechanical engineering experienced a surge of growth during the early 19 th century because it provided a necessary foundation for the rapid and successful development of industrial revolution At that time, mines needed large pumps never before seen to keep their drafts dry; iron and steel mills required pressures and temperatures beyond levels used commercially until then; transportation systems needed more than real horse power to move goods; structures began to stretch across ever wider abysses and to climb to dizzying heights; manufacturing moved from the shop bench to large factories Now, more than a century later, we are witnessing a new scientific and social revolution known as the information revolution, where engineering specialization ironically seems to be simultaneously focusing and diversifying To practice engineering today, we must understand new ways to process information and be able to utilize semiconductor electronics within our products, no matter what label we put on ourselves as practitioners The term mechatronics is used to denote a rapidly developing, interdisciplinary field o f engineering that deals with the design of products whose function relies on the systematic integration of mechanical, electrical, and electronic components connected by a control architecture It is one of the new and exciting fields on the engineering l andscape, subsuming parts of traditional engineering fields and requiring a broader approach to the design of systems that we can formally call mechatronic systems A mechatronic system designer must assemble analog and digital circuits, microprocessors an d computers, mechanical devices, sensors and actuators, and controls so that the final design achieves a desired goal Increasingly, digital circuits and microprocessors are embedded in electromechanical devices, creating much more flexibility and control possibilities in system design A fundamental part of many mechatronic systems is a measurement system that is composed of the three basic parts illustrated in Figure 1.1 The transducer is a sensing device that converts a physical input into an output, usually a voltage The signal processor performs filtering, amplification, or other signal conditioning on the transducer output The term sensor is often used to refer to the transducer or to the combination of transducer and signal processor Finally, the recorder is an instrument, a computer, a hardcopy device, or simply a display that maintains the sensor data for online monitoring or subsequent processing TRANSDUCER SIGNAL PROCESSOR RECORDER Fig.1.1 Elements of a measurement system EXERCISE B Vocabulary check through rephrasing Rewrite the following sentences, replacing the words in italic with expressions from the text above which have similar meanings A sudden increase in mechanical engineering occurred during the early 19 th century Engineering specialization ironically seems to be focusing and diversifying at the same time We need know how to use semiconductor electronics within our products This field of engineering is of covering more than one area of study These components are in a systematic combination If you are a mechatronic system designer, you must fit electromechanical and electronic equipment together in a system design EXERCISE C Fact check through questions Answer the following questions according to the text How many important revolutions are referred in the text? When were they? In what fields was the first one effective? (Focus on the punctuation for listing) Name basic equipment in a mechatronic system To what kind of engineering does it belong? (Focus on the bended word “mechatronic”) How many basic parts in a measurement system? EXERCISE D Grammar check – Reduced relative clauses Develop the expressions in italic into full clauses in your own ways Mines needed large pumps never before seen to keep their drafts dry Iron and steel mills required pressures and temperatures beyond levels used commercially until then Digital circuits and microprocessors are embedded in electromechanical devices, creating much more flexibility and control possibilities in system design It is one of the new and exciting fields on the engineering landscape, subsuming parts of traditional engineering fields and requiring a broader approach to the design of systems Word study WORD FORMATION 1-SUFFIXES When you are reading, you will come across unfamiliar words It is often possible to guess the meaning of these words if you understand the way the words in English are generally formed An English word can be divided into parts: a prefix, a stem, and a suffix Pre- means “before”, a prefix, therefore, is what comes before the stem A suffix, on the other hand, is what is attached to the end of the stem Both of them are referred to affixes (See more in Appendix ….) Suffixes change the part of speech of the word For example, -ly added to the adjective commercial gives the adverb commercially SUFFIXES MEANINGS EXAMPLES  Noun- forming suffixes: -ance state importance, resistance -ence quality of independence, existence -er /-or a person who / a thing which operator, amplifier -ation the act of application, operation -ist a person who chemist, dentist -ness condition of toughness, happiness -iron action / state corrosion, expansion -ing activity welding, drilling -ment state / action measurement, treatment -ily state / quality ductility, elasticity -ian pertaining to electrician, mathematician -ism condition / state magnetism -dom condition freedom -ship condition / state relationship, friendship -age state leakage, shrinkage -full containing lots of handful, teaspoonful  Verb- forming suffixes: -ize / -ise industrialize, liquidize -ate activate, calculate -fly to make solidify, amplify -en shorten, harden  Adjective- forming suffixes: -al -ar structural, axial have quality of circular, rectangular -ic / -ical hydraulic, logical -able / -ible capable of being flammable, combustible -ous / -ious like, full of ferrous, dangerous, obvious -full characterized by useful, colourful -less without useless, colourless -ish like childish, bookish -ed having coloured, reinforced, punched -ive quality of interactive, explosive -ing making or doing melting, processing EXERCISE E Read the following sentences and circle the suffixes Underline the stem if it can be used on its own The first one has been done for you A programmer designs, writes, and tests programs for performing various tasks on a computer A systems analyst studies organizational systems and decides what action needs to be taken to maximize efficiency Laser printers are preferable to other types of printing devices because of their speed and quietness The microcomputer we have purchased does not have a FORTRAN complier It is programmable in BASIC only We have found that operators who have the freedom to take short breaks during the day greatly improve their performance The number of shipments will increase over the coming months We decided to computerize the entire plant to give each division more independence Spooling is a way of storing data temporarily on disk or tape until it can be processed by another part of the system Turning your office into a paperless environment may be expensive at the beginning but can produce big saving in the long run 10 Software developers are producing increasingly sophisticated applications for a growing global market Now, for each word that has a suffix, indicate what part of speech the word is (e.g noun, verb, etc.) EXERCISE F Fill in each blank with the appropriate form of the word in brackets The (melt)……………point of a material has a number of indirect effects on (manufacture) ……………(operate) …………… The choice of a material for high temperature (apply) ……………is the most obvious (consider) ……………, such as with high (slide) ……………speeds of machine components (Slide) ……………down a rope or (rub) ……………you hands together (quick) ……………is a simple (demonstrate) …………… of how high temperatures can become with (increase) …………… (slide) ……………speed Language study EXPRESSING THE LINK Look at the following columns What is the link between column A and column B? A B mechanical machines electrical electricity Column A lists a branch of engineering or a type of engineer Column B lists things they are concerned with We can show the link between them in a number of ways: Mechanical engineering deals with machines Mechanical engineers deal with machines Mechanical engineering is concerned with machines Mechanical engineers are concerned with machines Machines are the concern of mechanical engineers EXERCISE G Match each item in the right column with an appropriate item from the left column and link the two in a sentence marine A air-conditioning aeronautical B roads and bridges heating and ventilating C body scanners electricity generating D cables and switchgear automobile E communications and equipment civil F ships electronic G planes electrical installation H cars and trucks medical I power stations Information transfer EXERCISE H Use information from the following text to complete the blanks in the diagram below ENGINEERING- WHAT‟S IT ALL ABOUT? Engineering is largely a practical activity Civil engineering is concerned with making bridges, roads, airports, etc Mechanical engineering deals with the design and manufacture of tools and machines Electrical engineering is about the generation and distribution of electricity and its many applications Electronic engineering is concerned with developing components and equipment for communications, computing, and so on Mechanical engineering includes marine, automobile, aeronautical, heating and ventilating, and others Electrical engineering consists of electricity generating, electrical installation, lighting, etc Mining and medical engineering belong partly to mechanical and partly to electrical Engineering Mechanical Marine Automobile Electrical Heating and ventilating Electricity generating Electrical installation Lighting Mining Guided writing Use information from the above diagram and the language you have studied in this unit to fill in the gaps in the following description The main branches of engineering are civil, _, _, and electronic Mechanical engineering is _ _ machinery of all kinds This branch of engineering includes _, _, aeronautical, and heating and ventilating The first three are _ with transport: _, cars and planes The last _ with air-conditioning, refrigeration, etc Electrical engineering deals with _ from generation to use Electricity generating is concerned with _ stations Electrical installation deals _ cables, switchgear, and connecting up electrical equipment Two branches of engineering are the _ _ both _ and medical engineers These are mining and medical engineering The former _ with mines and mining equipment, and the later with hospital _ of all kinds WORD LIST Unit 1 (V) & (N): increase suddenly and intensely E.g There’s a in electricity demand around p.m (N): unit for measuring the power of an engine (550 foot-pounds per second, about 750 watts) E.g A twelve engine (N): a hole so deep that it seems to have no bottom (V): be present at (sth) and see it (Adj) causing people feel as if everything is spinning around, unbalanced (V): include sth in a particular group or class (V): combine sth with sth (N): a circuit that operates like a switch in which it has only two states: either ON or OFF (N) & (Adj): a continuous representation of a physical phenomena, such as a signal 10 (N): (abbreviated to MPU) a central process unit on a single large integrated circuit chip, required for processing data UNIT ROBOTICS Warm-up Say what you think robots can Then have a quick look over the text to compare with your ideas AIBO (Artificial Intelligence roBOt) is a robot dog, developed by Sony He is 27.4 cm long, 26.6 cm high, and weighs 1.5 kilos You can control him with a computer, a remote control, or with voice instructions AIBO is not just a toy Sony developed and tested him as an electronic friend for old people Here are some things AIBO can  walk and run backwards and forwards  stand on his back legs and raise and lower his front legs  see and remember things  understand the name you give him  dance  understand 75 different voice instructions (Sit! Come! No!, etc.)  take photographs  make robotic dog sounds  learn new actions Listening Describing robots Pre-listening Complete the sentences with the words given in the box austronaut radioactive nuclear power reactors vacuum gripper pallets A _ is a robot component that can lift and handle objects Radium and uranium are _ elements The explosion of one of four Chernobyl _ on April 26, 1986 is the worst such accident to date 22 In the warehouses, goods are often loaded on _ as clean, level surfaces and easily moved by fork-lift trucks Valentina Tereshskova was the world‟s first woman _ Whlie-listening Listen to different people talking about robots Number the photos in the order you hear about them Post-listening Check your listening by answering the questions Which robot: - is fully automatic? - can reach 15 meters? - is an electronic pet? - has vacuum gripper feet? - is the solution for dirty windows? - is designed to save floor space? Reading skill Dealing with unfamiliar words Guessing meaning from context It is advised to ignore unfamiliar words which not help our reading purpose However, some words we can not ignore, but often an approximate rather than exact meaning of a word is all that is required Sometimes we can work out the approximate meaning of a word from its context Look at the sentence as an example Because they have no wheels, axles, suspension, dampers, or brakes, Maglev trains are light and compact We can say that dampers are probably: - heavy (not light) - large (not compact) 23 - part of the undercarriage (same set as wheels, axles, suspension, and brakes) EXERCISE A Try to work out the approximate meaning of any of the words printed in bold in the following text whose meaning you not already know Check your answers with a dictionary When first introduced, linear motors were seen as a major technological breakthrough However, disappointingly few practical applications have been found for this new development An earlier innovation, the Wankel engine, was radically different from conventional engines, having a rotary piston and no valves Wankel engines were adopted by the Mazda car company However, Wankel engines are now rarely used because of problems with fuel consumption and maintenance Reading and Comprehension Fig 3.1 The components of an industrial robot The manipulator This is the bit which actually does the mechanical work, and in this case it is anthropomorphic (i.e of human-like form), resembling an arm 24 The power supply For heavy-duty hydraulic or pneumatic machines this will be a compressor In smaller, lightweight versions which use electrical stepper motors rather than hydraulics or pneumatics, this would be omitted The computer The controlling computer is fitted with appropriate interfaces These may include digital inputs, digital outputs, ADCs (analog- to –digital converters), DACs (digital-analog converters), or stepper motor control ports These control the various compressors, stepper motors, and solenoids, and receive signals from the manipulator‟s sensors Work volume Robots are multifunctional so an important design issue for the manipulator is its „work volume‟: the volume of space into which it can be positioned The greater the work volume, the more extensive the range of tasks it can be programmed to carry out As a human being, your work volume consists of all the places your hands can reach Most industrial robots have a much more limited work volume because they are bolted to the floor Even with the same limitation applied, however, the human body is a very flexible machine with a work volume described – very approximately – by a cylinder about 2.2 m high with a radius of about 1.8 m and a domed top Degrees of freedom In order to achieve flexibility of motion within a three-dimensional space, a robot manipulator needs to be able to move in at least three dimensions The technical jargon is that it requires at least three „degrees of freedom‟ Figs 3.2 a-d shows a number of the more common types of robot manipulator mechanisms Each has the requisite three degrees of freedom, allowing either linear or rotational movement EXERCISE B Answer the questions 25 What are the functions of the three components of an industrial robot shown in Fig 3.1? What is the work volume of a manipulator? What is the work volume of a human? Why is the work volume of a human greater than that of an industrial ro bot? What are „degrees of freedom‟? Word study COMPOUND NOUNS We can use adjectives to describe an object in greater detail For example: a motor an electric motor steel stainless steel gears helical gears We can also use nouns For example: light laser light a motor an air motor steel carbon steel gears titanium gears The language of engineering in English contains an ever-increasing number of compound nouns, that is, a group of two or more nouns which act as a single noun Examples: control system address bus bar code scanner It is important to be able to recognize how such compounds are formed in order to understand what they mean The exact relationship between the words depends on the particular expression, but all these expressions have one thing in common: the last word in the chain says what the thing is, while the preceding word or group of words describe the thing So when we read compound nouns, we have to start with the last word and work backwards Example: A hardness tester is (a device) used to test the hardness (of a product) 26 A large number of possible meanings can be expressed by compound nouns For instance, the first noun or group of nouns can tell us what the second noun is made of, what it is for, or what it is part of Material: the first noun tells us what the second consists of Examples: - a silicon chip (a chip made of silicon) - a plastic pipe (a pipe made of plastic) Function: the first noun tells us what the second is for Examples: - an input device (a device for inputting) - a battery charger (a device for charging battery) Part: the second noun refers to a part of the first noun Examples: - a monitor screen (the screen of a monitor) - a computer keyboard (the keyboard of a computer) Activity or person: the second noun refers to an activity or person related to the first noun Examples: - a computer programmer (a person who programs computers) - grid emission (the emission - of electron or ion - from a grid - of an electron tube) Others: Many other relationships are possible in noun compounds Examples: - an air motor (a motor which uses air) - carbon steel (steel which contains carbon) - a foot pump (a pump which is operated by foot) - a ribbon cable (a cable which is like a ribbon) Multiple nouns: Sometimes a compound noun will join together with one or more other nouns to give an expression that has three or four words In such cases, it is 27 important to examine the expression very carefully to break it into its constituent parts The secret, as always, is to read the expression from the back towards the front Examples: - a document image processing program (a program which processes images of documents) - an all-wheel antilock brake system (a safety system which prevents all the road wheels on a motor vehicle from locking up – ceasing to rotate – while braking) NOTE: Some expressions are written separately, while others are joined by hyphens There are no clear rules for this Sometimes you will see the same expression written in different ways in different text EXERCISE C Describe the relationships in the following noun compounds carbon blocks a circuit boards aluminium alloy steel sheets carbon fibre a power tool a gas burner 10 a ball bearing roller bearing 11 a diesel boat a spring balance 12 a gear lever EXERCISE D Describe the relationships in the following noun compounds chain wheel tool steel disc brake boiler thermostat foot brake safety helmet strain gauge boiling curve spring clip 10.vacuum gripper 28 EXERCISE E Explain the following noun grpous camera autofocus system system design engineering control system programs computer-machine controls wind turbine machinery content material handling instructions legacy weapon systems parts aircraft engine turbine blades EXERCISE F Name these objects / systems which are used to: reduce the speed (of a motor) indicate the level of oil (in a gear box) grind the surface (of a metal plate) inject fuel (into petrol or diesel engines) filter oil (for an engine) cut wires sense moisture (in an environment) compress air convert digital (signals) to analogue (signals) 10 package products automatically Language study EXPRESSING THE CONCESSION (even if and although) We can use if to link two statements like this: The switch is on The lamp lights If the switch is on, the lamp lights 29 When statement is true, statement is also true When statement surprisingly has no effect on statement 2, we can use even if or although For example: The switch is on The lamp does not light Even if the switch is on, the lamp does not light Although the switch is on, the lamp does not light EXERCISE G A car is fitted with a seat belt warning light The light operates under these conditions: Seats occupied Ignition Belt Light Yes On Closed Off Yes On Open On Yes Off Closed Off No Off Closed Off Study these examples of normal and faulty operation: Normal: If the seat is occupied, the ignition on and the belt closed, the light is off Faulty: Even if the belt is closed, the light stays on Although the belt is closed, the light stays on Now give other examples of normal and faulty operation of this circuit Speaking Pairwork – Using the flowchart Flowcharts are pictorial representations of a process By breaking the process down into its constituent steps, flowcharts can be useful in identifying where errors are likely to be found in the system 30 Look at the following chart Work in pairs for a logical approach to finding the fault Try to make a conversation between an instructor and an apprentice Information transfer Transfering information to a table A table is commonly used as a means to layout document content As a scientific communication tool, it allows a form of generalization of information from an unlimited number of different contexts It provides a familiar way to convey information that might otherwise not be obvious or readily understood EXERCISE H Read the following text and complete the table below COMMON TYPES OF MANIPULATOR Fig 3.2.a is the simplest Its three degrees of freedom are on linear and at right angles to each other, so they correspond to the three Cartesian co-ordinates Driving it presents no mathematical difficulties, since each degree of freedom controls a single Cartesian co ordinate without affecting the others Fairly obviously, the work volume of the Cartesian manipulator is a cube 31 Fig a Cartesian or rectilinear manipulator The second type of manipulator, shown in Fig 3.2.b, is called a cylindrical manipulator because of the shape of its work volume It has one rotational and two linear degrees of freedom Because of rotational respect, however, the maths needed to position it becomes more involved, which means that for a given response speed a faster processor is necessary Fig b Cylindrical or post-type manipulator Fig 3.2.c shows the spherical manipulator which has two rotational and one linear degree of freedom The work volume is indeed a sphere, and once again the complexity of positioning the device increases 32 Fig c Spherical or polar manipulator The final type of manipulator has three rotational degrees of freedom This is the most complex type to control, but it has increased flexibility Fig 3.2.d shows this type of manipulator – the anthropomorphic arm The work volume of a practical manipulator of this form is shown in Fig 3.2.e You will notice that it is basically spherical but has missing portions due to the presence of the arm itself and because the rotations cannot achieve a full 360 degrees The scallops on the inner surface are caused by constraints imposed by the joints Fig d Fig e Anthropomorphic or joint manipulator The work volume of an anthropomorphic manipulator 33 Degrees of freedom Figure Type Linear rotationa Work volume l 3.2.a Cartesian or rectilinear cube 3.2.b 3.2.c 3.2.d Guided writing Complete each blank in the following text with ONE suitable word MECHANICAL WRIST It is worth pointing _ that a human arm has arm far more freedom _ the minimum three degrees of freedom, giving very great flexibility in terms _ positioning, path taken, and angle of approach Even without a wrist, the redundant degrees of freedom of the body would allow you to carry out most normal operations Any of the basic manipulators shown _ Figs.3.2a-d, on the other _, would be virtually useless as they stand Although they could get to any position, they _ only approach objects from a single angle To take an _, removing a screw would be impossible _ the manipulator could not align a screwdriver to fit the screw properly Even if it was able to, it still would _ be possible to carry out the necessary rotating action A wrist is therefore added to most basic manipulators to _ the required mechanical flexibility to real jobs In general, for total flexibility the wrist itself requires three degrees of freedom, thereby bringing the grand total up to six The _ common type of wrist has t wo bending and one rotational degree of freedom Fig 3.4 shows this type of mechanical wrist 34 Fig 3.4 A typical mechanical wrist Summarizing Read the following text and match each robot type with the appropriate definition TYPES OF ROBOTS One way of classifying robots is in terms of their similarity to humans An automation is any machine capable of operating independently, such as clothes dryer A flexible machine is a special case of automation with different capabilities, that can be programmed as the need arises An example is a welding robot on the factory floor that can be programmed to participate in other production operations A mobile robot is a flexible machine capable of moving freely in its own environment It can partly select its own goals and communicates with other agents, including humans An android or humanoid is a mobile robot whose structure approximately resembles a human structure Finally, a cyborg is a humanoid with organic structures Cyborgs have some physiological structures similar to those of humans Mobile robot Cyborg Automation Flexible machine Android / Humanoid A Machine capable of independent operation following a predetermined series of behaviours, e.g a cuckoo clock B Flexible machine capable of moving and communicating with humans, e.g a sentry robot C Humanoid having both organic and inorganic structures, with some physiological similarity to humans D Mobile robot of human proportions E Versatile, programmable automation E.g an assembly robot 35 36 [...]... material in a very precise way They can be used for drilling diamonds, cutting complex shapes in materials from plastics to steel, for spot welding and for surfacing techniques, such as hardening aircraft engine turbine blades Laser beams can also be used to measure and align structures Lasers are ideal for communications in space Laser light can carry more information channels than microwaves because of... can be used for drilling diamonds 3 They can be used for light displays When we ask about the functions of some device, we can use the following structures: What does it do? What is its function? What is it for? To give the explanation, we can say: It + verb It is used to + infinitive It is used for + gerund / noun It is used as + noun Its function is to + infinitive EXERCISE E Use the information in... water pumped out Finally, the clean clothes are removed EXERCISE G Study this diagram It shows an extruder for forming plastic pipes Now put these stages in the process in the correct sequence a The hot plastic is forced through the die to form a continuous length of pipe b The rotating screw forces the plastic past heaters c The plastic granules are mixed and placed in the hopper d The pipe is cooled... system 30 Look at the following chart Work in pairs for a logical approach to finding the fault Try to make a conversation between an instructor and an apprentice Information transfer Transfering information to a table A table is commonly used as a means to layout document content As a scientific communication tool, it allows a form of generalization of information from an unlimited number of different... compound nouns For instance, the first noun or group of nouns can tell us what the second noun is made of, what it is for, or what it is part of 1 Material: the first noun tells us what the second consists of Examples: - a silicon chip (a chip made of silicon) - a plastic pipe (a pipe made of plastic) 2 Function: the first noun tells us what the second is for Examples: - an input device (a device for inputting)... used for information recording and reading Compact discs are read by laser In medicine, laser beams can treat damaged tissue in a fraction of a second without harming healthy tissue They can be used in very precise eye operations In the arts, lasers can provide fantastic displays of light Pop concerts are often accompanied by laser displays EXERCISE B Complete this table of laser applications using information... automatically 4 (V) place or arrange thing(s) in a straight line 5 (N) a band of radio frequencies; a path for data transmitted 6 (N) a thin circular object, such as a phonograph record or a metal or plastic sheet having a magnetic or other type of coating, used for storing computer data or video information (sometimes spelled disc)  (N) It has sound recorded as laser generated microscopic pits on a... the pits, is converted back to a reproduction of the original sound It is a red-only memory (ROM) A player plays it back and the signal is amplified for headphones or speaker 7 (V) force or squeeze out sth (e.g plastic, metal) under pressure through a die for shaping (N) small hard piece; small grain 21 UNIT 3 ROBOTICS Warm-up Say what you think robots can do Then have a quick look over the text to compare... Word study COMPOUND NOUNS We can use adjectives to describe an object in greater detail For example: a motor an electric motor steel stainless steel gears helical gears We can also use nouns For example: light laser light a motor an air motor steel carbon steel gears titanium gears The language of engineering in English contains an ever-increasing number of compound nouns, that is, a group of two or... that can be processed by the system 12 (N): devices used to produce the motion or action in a mechatronic system, which is crated by a force or torque that results in acceleration and displacement 13 (N): a general term for any device that converts energy from one form to another, as from sound energy to electric or mechanical energy Some examples of this are loudspeakers, microphones, recording heads…