信息科學(xué)與電子工程專業(yè)英語(yǔ)課后答案

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1、Unit 1 Exercises (1) Translate the following sentences into Chinese. 1. As with series resonance, the greater the resistance in the circuit the lower the Q and, accordingly, the flatter and broader the resonance curve of either line current or circuit impedance. 對(duì)于串聯(lián)諧振，電路中的電阻愈大Q值就愈低，相應(yīng)地線路電流或電路阻抗的

2、諧振曲線也就愈平、愈寬。 2. A wire carrying a current looks exactly the same and weighs exactly the same as it does when it is not carrying a current. 一根帶電的導(dǎo)線其外表與重量都與不帶電導(dǎo)線完全一樣。 3. Click mouse on the waveform and drag it to change the pulse repetition rate, or directly enter a new value of the period in t

3、he provided dialogue box, while keeping the pulse width unchanged. 在波形上點(diǎn)擊鼠標(biāo)并拖動(dòng)來(lái)改變脈沖重復(fù)頻率，或者在提供的對(duì)話框中直接輸入新的周期值，而保持脈沖寬度不變。 4. Electronics is the science and the technology of the passage of charged particles in a gas, in a vacuum, or in a semiconductor. Please note that particle motion confined wit

4、hin a metal only is not considered electronics. 電子學(xué)是一門有關(guān)帶電粒子在氣體、真空或半導(dǎo)體中運(yùn)動(dòng)的科學(xué)技術(shù)。注意，在本書中粒子運(yùn)動(dòng)僅限于金屬的情況不屬于電子學(xué)。 5. Hardware technologies have played vital roles in our ability to use electronic properties to process information, but software and data processing aspects have not developed at the same s

5、peed. 硬件技術(shù)在我們使用電子特性來(lái)處理信息的能力中一直起著重要作用，而軟件及數(shù)字處理方面卻沒(méi)能與硬件同步發(fā)展。 6. However, in a properly designed DC amplifier the effect of transistor parameter variation, other than Ico, may be practically eliminated if the operation point of each stage is adjusted so that it remains in the linear operation range

6、 of the transistor as temperature varies. 然而在設(shè)計(jì)得當(dāng)?shù)闹绷鞣糯笃髦校粽{(diào)節(jié)每一級(jí)的工作點(diǎn)使之在溫度變化時(shí)保持在晶體管線性區(qū)，就能在實(shí)際上消除Ico以外的晶體管參數(shù)變化所造成的影響。 Unit 2 Exercises (1) Translate the following sentences into Chinese. 1. If analog signals are to be transmitted digitally, they first have to be sampled at a specified rate and furt

7、her converted to discrete amplitude samples by quantization. 如果要以數(shù)字方式傳輸模擬信號(hào)，首先必須以一定的頻率對(duì)信號(hào)進(jìn)行采樣，然后通過(guò)量化進(jìn)一步將它們轉(zhuǎn)換為離散的幅度樣本。 2. Linear filters amplify or attenuate selected spatial frequencies, can achieve such effects as smoothing and sharpening, and usually form the basis of re-sampling and boundary

8、detection algorithms. 線性濾波器放大或衰減選擇的空間頻率，能夠?qū)崿F(xiàn)像平滑和銳化這些效果，通常是重采樣和邊緣檢測(cè)算法的基礎(chǔ)。 3. Stability and repeatability are fundamental attributes of digital circuits, however, and the necessary accuracy can be obtained in a digital version of the modulator by an appropriate choice of word length to repre

9、sent the signals. 不過(guò)穩(wěn)定性和可重復(fù)性是數(shù)字電路的基本性質(zhì)，在數(shù)字式調(diào)制器中必要的精度可通過(guò)適當(dāng)?shù)剡x擇代表信號(hào)的字長(zhǎng)而獲得。 4. The first observation is made on the fundamental relationship between the nature of system and the periodicity of its frequency response: a continuous system has an aperiodic frequency response, while a discrete system ha

10、s a periodic frequency response. 從系統(tǒng)性質(zhì)和它頻率響應(yīng)的周期性之間的基本關(guān)系中首先可以看到：連續(xù)系統(tǒng)有非周期性的頻率響應(yīng)，而離散系統(tǒng)有周期性的頻率響應(yīng)。 5. The main function of the receiver is to extract the input message signal from the degraded version of the transmitted signal coming from the channel. 接收器的主要功能是從由信道傳輸來(lái)的退化了的信號(hào)中提取出輸入消息。 Unit 3 Exerc

11、ises (1) Translate the following sentences into Chinese. 1. A very commonly used method of microwave measurements is based on the study of a standing wave pattern formed along the line because of the interference of incident and reflected waves. 一個(gè)很常用的微波測(cè)量方法是基于對(duì)駐波圖型的研究，這種駐波是由入射波和反射波之間的干涉而沿著傳輸線形成的

12、。 2. Computations show a reduction of 6dB in the EM field intensity with the distance doubled, and an increase of 3dB in the intensity with the transmitted power doubled. This result provides verification to the algorithm used. 計(jì)算表明，當(dāng)距離增大一倍時(shí)，電磁場(chǎng)強(qiáng)度減小6分貝；而發(fā)射功率增大一倍時(shí)，場(chǎng)強(qiáng)則增加3分貝。這一結(jié)果驗(yàn)證了所用算法的正確性。 3.

13、Like transfer of heat by conduction, convection and radiation, microwave heating can be considered as another mode of heat transfer, in which heat is produced directly at the location of the dielectric losses. 就像通過(guò)傳導(dǎo)、對(duì)流、輻射來(lái)傳遞熱量一樣，微波加熱可以看作熱傳遞的另一種方式，即熱量直接產(chǎn)生于發(fā)生介電損耗的地方。 4. Operation of the radar is

14、 based on the measurement of the time it takes for a pulse transmitted from an antenna to get reflected by the object to be detected and to return at the antenna and the receiver. 雷達(dá)的工作是基于對(duì)天線發(fā)出的脈沖被所要探測(cè)的目標(biāo)反射，（然后）回到天線和接收機(jī)所需時(shí)間的測(cè)量。 5. Other motivations for using CAD in circuit design includes the wi

15、sh to acquire confidence in a design that was accomplished by other means, and, not least in importance, a sense of curiosity or perhaps a desire to discover the unexpected. 在電路設(shè)計(jì)中使用CAD的其它動(dòng)機(jī)包括：想要驗(yàn)證用別的方法設(shè)計(jì)出來(lái)的電路；滿足好奇心或者可能是想發(fā)現(xiàn)預(yù)想不到的現(xiàn)象。后一個(gè)動(dòng)機(jī)并非是最不重要的。（取得信心，并非最不重要，意料之外的事） 6. The spacing between the rep

16、eating amplifiers is a function of the cable attenuation and the system bandwidth so that the gain provided by these amplifiers compensates for the loss introduced by the cable. 中繼放大器之間的間距是電纜衰減和系統(tǒng)帶寬的函數(shù)，以便這些放大器提供的增益補(bǔ)償電纜引起的損耗。 7. When the cut-off frequency is no less than the maximal frequency of

17、the original signal, nor is it greater than the difference between the sampling frequency and the maximal frequency, the original signal may be completely rebuilt. 當(dāng)截止頻率不小于原始信號(hào)的最高頻率，也不大于采樣頻率和最高頻率之差，原始信號(hào)可以完整地重建。 8. While the politics of the last one hundred years centered around Industrial Age te

18、chnology, the politics of the future will be based on Information Age concerns oriented towards the storage, protection and exchange of information. 盡管近百年來(lái)的政治活動(dòng)是以工業(yè)時(shí)代的技術(shù)為中心的，未來(lái)的政治活動(dòng)將基于信息時(shí)代的事物，面向信息的存儲(chǔ)、保護(hù)和交換。 Unit 4 Exercises (1) Translate the following passages into Chinese. 1. Communication ma

19、y be broadly defined as the transfer of information from one point to another. When the information is to be conveyed over any distance a communication system is usually required. Within a communication system the information transfer is frequently achieved by superimposing or modulating the informa

20、tion on to an electromagnetic wave which acts as a carrier for the information signal. This modulated carrier is then transmitted to the required destination where it is received and the original information signal is obtained by demodulation. Sophisticated techniques have been developed for this pr

21、ocess by using electromagnetic carrier waves operating at radio frequencies as well as microwave and millimeter wave frequencies. However, communication may also be achieved by using an electromagnetic carrier that is selected from the optical range of frequencies. 通信可以廣義地定義為從一處到另一處的信息傳遞。當(dāng)要將信息傳輸?shù)饺魏?/p>

22、距離以外時(shí)就需要有一個(gè)通信系統(tǒng)。在通信系統(tǒng)內(nèi)部，信息的傳輸經(jīng)常通過(guò)將信息疊加或調(diào)制到作為信號(hào)載體的電磁波上來(lái)實(shí)現(xiàn)。經(jīng)調(diào)制的載波然后被傳送到要求的目的地，在那里被接收，原始信號(hào)通過(guò)解調(diào)被恢復(fù)出來(lái)。為了實(shí)現(xiàn)這一過(guò)程，已經(jīng)利用工作在射頻、微波以及毫米波頻率上的電磁載波開(kāi)發(fā)了復(fù)雜的技術(shù)。不過(guò)通信也可以用光波頻段上的電磁載波來(lái)實(shí)現(xiàn)。 2. Electronic communications is the transfer and movement of data between locations through the use of computers. An electronic commun

23、ication system includes the equipment needed to support the movement of information, the communication lines and media to carry the information, the computer software and programs to control the flow of information, the personnel to plan, implement, and operate communications, and the management of

24、all these resources. Electronic communications establishes links between people as well as computers. 電子通信就是通過(guò)使用計(jì)算機(jī)在不同的地點(diǎn)之間傳輸數(shù)據(jù)。一個(gè)電子通信系統(tǒng)包括：支持信息流動(dòng)所需要的設(shè)備，承載信息的通信線路和媒介，控制信息流的計(jì)算機(jī)軟件和程序，計(jì)劃、實(shí)施、操作通信系統(tǒng)的人員，以及對(duì)所有這些資源的管理。電子通信建立起人和人、計(jì)算機(jī)和計(jì)算機(jī)之間的聯(lián)系。 3. First generation communications systems can be characterize

25、d by the use of analog transmission techniques, and the use of simple multiplex access techniques such as frequency division multiple access (FDMA). They suffered from a low user capacity, and security problems due to the simple radio interface used. Second generation systems were introduced in the

26、early 1990’s, and all use digital technology. This provided an increase in the user capacity of around three times, achieved by compressing the voice waveforms before transmission. Third generation systems are an extension on the complexity of second-generation systems and are to be introduced after

27、 the year 2000. The system capacity will be increased to over ten times original first generation systems, achieved by using complex multiplex access techniques such as code division multiplex access (CDMA), or an extension of TDMA, and by improving flexibility of services available. 第一代通信系統(tǒng)以模擬傳輸技術(shù)

28、和簡(jiǎn)單復(fù)用技術(shù)如頻分復(fù)用為特征。這些系統(tǒng)用戶容量低，而且因?yàn)槭褂煤?jiǎn)單的無(wú)線電接口而存在安全問(wèn)題。第二代通信系統(tǒng)于20世紀(jì)90年代初開(kāi)始引入，全部使用數(shù)字技術(shù)。通過(guò)在傳輸前將話音波形壓縮使得用戶容量提高了三倍。第三代通信系統(tǒng)是對(duì)第二代系統(tǒng)在復(fù)雜性方面的擴(kuò)展，預(yù)計(jì)于2000年以后啟用。通過(guò)使用復(fù)雜的復(fù)用技術(shù)如CDMA或TDMA的擴(kuò)展，并提高服務(wù)的靈活性使得系統(tǒng)容量比原來(lái)的第一代系統(tǒng)提高10倍。 4. For each combination of communication (modulation/detection) type, channel fading model, and dive

29、rsity type, the average bit error rate (BER) and/or symbol error rate (SER) of the system is obtained and represented by an expression in a form that can readily be evaluated. All cases considered correspond to real practical channels, and in many instances the BER and SER expressions obtained can b

30、e evaluated numerically on a hand-held calculator. 對(duì)于通信（調(diào)制/檢測(cè)）類型、信道衰落模型、分集類型的每一種組合，得到系統(tǒng)的平均誤碼率（BER）和符號(hào)錯(cuò)誤率（SER），并以容易求值的形式表示。所有考慮的相應(yīng)于實(shí)際信道的情況，以及許多情況下得到的BER和SER表達(dá)式均可用手持計(jì)算器來(lái)計(jì)算。 5. Modulation is the systematic variation of some attribute of a carrier waveform such as the amplitude, phase, or frequency

31、in accordance with a function of the message signal. It is used in communication systems for matching signal characteristics to channel characteristics, for reducing noise and interference, for simultaneously transmitting several signals over a single channel, and for overcoming some equipment limit

32、ations. A considerable portion of this book is devoted to the study of how modulation schemes are deigned to achieve the above tasks. The success of a communication system depends to a large extent on the modulation. 調(diào)制是載波波形的某些屬性，例如幅度、相位和頻率，根據(jù)消息信號(hào)的函數(shù)有規(guī)則的變化。它用于通信系統(tǒng)以使信號(hào)特性匹配信道特性，減少噪聲和干擾，在單個(gè)信道上同時(shí)傳輸多個(gè)信號(hào)

33、，并克服某些設(shè)備的限制。本書相當(dāng)大部分內(nèi)容是研究如何設(shè)計(jì)調(diào)制方案以實(shí)現(xiàn)上述任務(wù)。一個(gè)通信系統(tǒng)的成功很大程度上依賴于調(diào)制。 Unit 5 Exercises (1) Translate the following passage into Chinese. OFDM consists of a large number of subcarriers equally spaced in a frequency band, each may be digitally modulated by a same scheme such as PSK, QAM, etc., or by diffe

34、rent schemes. A serially transmitted sequence is divided into a number of sections, each having N symbols, and the N symbols in each section are used to modulate N carriers for simultaneous transmission. Therefore OFDM is essentially a parallel modulation system. When the number of subcarriers is su

35、fficiently large, the system can resist multipath interference. This is because that, in the time domain, a symbol duration longer than the multipath delay can be chosen, while in the frequency domain, each symbol only occupies a small portion of the channel’s frequency band. Thus, the effect of mul

36、tipath fading spreads over many symbols, resulting in slight distortion to many symbols rather than complete destroy of a few symbols. In this way, correct demodulation is not affected so that the signal can be accurately recovered at the receiver. In an OFDM system, the principle of choosing the

37、subcarrier interval is to make the subcarriers mutually orthogonal within the entire symbol period. Thus, even if spectral overlap exists between the subcarriers, the symbols can still be recovered without loss. In order to realize maximum spectral efficiency, the interval between subcarriers is usu

38、ally chosen to equal the reciprocal of the symbol duration T. Therefore the subcarrier frequencies in the base band are fn = n/T, (n = 0, 1, ... , N-1). Denoting the n-th modulating symbol as X(n), the OFDM waveform within a symbol duration can be expressed as: (1) Sampling this waveform at t =

39、T/N yields (2) It is observed from the above expression that x(k) and X(n) form a discrete Fourier transform pair, therefore the baseband OFDM waveform can be generated from the discrete Fourier transform of N modulating symbols. When N=2m where m is an integer, the fast algorithm of IDFT is eas

40、y to implement. OFDM由大量在頻率上等間隔的子載波構(gòu)成。每個(gè)子載波可用同樣的方案，如PSK，QAM等，或者用不同的方案數(shù)字調(diào)制。將串行傳輸?shù)姆?hào)序列分成許多段，每一段有N個(gè)符號(hào)，每段的N個(gè)符號(hào)被用來(lái)分別調(diào)制N個(gè)載波同時(shí)發(fā)送。因此，OFDM本質(zhì)上是一個(gè)并行調(diào)制系統(tǒng)，當(dāng)載波數(shù)足夠大時(shí)，這種系統(tǒng)具有抗多徑干擾的能力。這是因?yàn)樵跁r(shí)域上符號(hào)周期能選取得比多徑延遲時(shí)間長(zhǎng)，而在頻域上每個(gè)符號(hào)只占整個(gè)信道帶寬的一小部分，因此多徑衰落的影響被分散到許多符號(hào)上，其結(jié)果是許多符號(hào)都發(fā)生輕度的畸變，而不是使某些符號(hào)被完全破壞。這樣，不影響正確的解調(diào)，信號(hào)能在接收器中準(zhǔn)確地恢復(fù)。 在OFDM系

41、統(tǒng)中，選擇子載波間隔的原則是使子載波在整個(gè)符號(hào)周期內(nèi)相互正交，這樣。即使在子載波間存在頻譜部分重疊，符號(hào)仍能無(wú)損失地恢復(fù)。為了實(shí)現(xiàn)最大的頻譜效率，子載波之間的間隔通常選取為符號(hào)周期的倒數(shù)。因此基帶子載波頻率為fn = n/T, (n = 0, 1, ... , N-1)，第n個(gè)調(diào)制符號(hào)記為X(n)，在一個(gè)符號(hào)周期內(nèi)的OFDM波形可表示： (1) 在t = T/N 時(shí)刻采樣這個(gè)波形得到： (2) 從上面的表示中可以看到，x(k) 和X(n)構(gòu)成了一對(duì)離散傅里葉變換，因此基帶OFDM波形可根據(jù)N個(gè)調(diào)制符號(hào)的離散傅里葉變換來(lái)生成。當(dāng)N=2m，其中m為整數(shù)，IDFT的快速算法很容易實(shí)現(xiàn)。

42、 Unit 6 Exercises (1) Translate the following sentences into Chinese. 1. Communication is the transmission of information from one point to another. This transmission requires the ability to vary signals with time in a manner which is unpredictable to the receiver. 通信就是信息從一點(diǎn)傳送到另一點(diǎn)。這種傳送要求信號(hào)隨時(shí)間發(fā)生的

43、變化不能在接收端預(yù)測(cè)。 2. It is true of any communication system that the shape and amplitude of the transmitted signal will be continuously degraded by the introduction of noise, and the attenuation along the transmission path. 傳輸?shù)男盘?hào)會(huì)不斷地被噪聲的引入和線路上的衰減所損傷，對(duì)任何通信系統(tǒng)都是如此。 3. Since the very beginning, communicati

44、ons systems have consisted of three major parts, namely, the equipment, the medium, and the protocol. It is still the case today. However, the close link of telecommunications with the computer technology has brought about tremendous changes in communications, from the concepts, to the contents and

45、the methods. 從一開(kāi)始通信系統(tǒng)就由設(shè)備、媒介和協(xié)議三個(gè)要素組成。至今依然如此。然而電信與計(jì)算機(jī)技術(shù)的緊密聯(lián)系使得通信從概念到內(nèi)容和手段都發(fā)生了重大的變化。 4. The availability of such a large collection of system performance curves in a single compilation allows the researcher or system designer to perform trade-off studies among the various communication type/fading

46、channel/diversity combinations so as to determine the optimum choice in the face of his or her available constraints. 在一本書中提供如此大量的系統(tǒng)性能曲線，使研究者或系統(tǒng)設(shè)計(jì)者能在各種通信類型、衰落信道、分集組合之間進(jìn)行比較研究，從而在他或她所面臨的限制之下做出最佳的選擇。 5. The channel provides the electrical connection between the information source and the user. The ch

47、annel can have many different forms such as a microwave radio link over free space, a pair of wires, or an optical fiber. 信道提供信息源和用戶之間的電路聯(lián)接。信道可以有許多不同的形式，比如自由空間里的微波聯(lián)接，一對(duì)電線，或者一根光纖。 6. The degradation of the transmitted signal is a result of signal distortion due to imperfect response of the channel

48、and due to undesirable electrical signals (noise) and interference. Noise and signal distortion are two basic problems of electrical communication. 傳輸信號(hào)的退化是信號(hào)失真的結(jié)果，而這種失真又是由信道的非理想響應(yīng)及不想要的電信號(hào)（噪聲）和干擾引起的。噪聲和信號(hào)畸變是電子通信的兩個(gè)基本問(wèn)題。 Unit 8 Exercises (1) Translate the following sentences into Chinese. 1. Ear

49、ly in the twentieth century, it was found that light could cause atoms to emit electrons and that, when light released an electron from an atom, the energy possessed by the electron very greatly exceeded that which the atom could, according to the electromagnetic wave theory, have received. 在二十世紀(jì)早期

50、，人們發(fā)現(xiàn)光能夠使原子放出電子，而且當(dāng)光從原子中釋放一個(gè)電子時(shí)，電子所包含的能量大大超過(guò)由電磁波理論得到的原子所接收的能量。 2. Pulse broadening determines the minimum separation between adjacent pulses, which in turn determines the maximum information-carrying capacity of the optical fiber. 脈沖的展寬決定了相鄰脈沖之間的最小間隔，這一間隔進(jìn)而又決定了光纖的最大信息容量。 3. If one were to transmi

51、t such information without impressing it on an optical carrier but instead on a radio frequency (RF) carrier a bit higher than the maximum rate, the transmission wavelength of the RF carrier would be centimeters or larger. 如果傳輸這樣的信息不是將它加載到光纖上，而是加載在略高于最大速率的射頻載波上，則此射頻載波就會(huì)是厘米波或是波長(zhǎng)更長(zhǎng)一些的波。 4. The small

52、ness of the optical wavelength, therefore, allows for the miniaturization of transmit and receive modules, which should allow considerable reduction in size, weight, and cost of optical communication systems with respect to microwave/radio wave counterparts. 光波波長(zhǎng)之小使發(fā)射和接收模塊得以小型化，這就使光通信系統(tǒng)的尺寸、重量以至價(jià)格與相

53、應(yīng)的微波、無(wú)線電波通信系統(tǒng)相比都大為降低。 5. Although all the advantages of coherent optical communication systems have yet to be brought to fruition, another property of optical radiation has made today’s optical communication systems not desirable for applications. 雖然相干光通信系統(tǒng)的所有優(yōu)點(diǎn)還有待于落實(shí)在具體成果中，光輻射的另一性質(zhì)卻使目前的光通信系統(tǒng)不利于應(yīng)用

54、。 6. When coupled with light’s short wavelength which allows for miniature sources and detectors and micron-sized waveguides, direct detection schemes have allowed for small, lightweight, high bandwidth systems which are competitive in many areas, most notably to the present telecommunications tran

55、smission, although a myriad of other applications are continually opening up. 光的波長(zhǎng)很小，可以使用小型的光源和檢測(cè)器以及微米級(jí)的波導(dǎo)，于是用直接檢測(cè)方案可實(shí)現(xiàn)在許多領(lǐng)域具有競(jìng)爭(zhēng)力的小巧的寬帶系統(tǒng)，這些領(lǐng)域中特別引人注目的是當(dāng)前電信傳輸中的應(yīng)用，盡管無(wú)數(shù)其他應(yīng)用也在不斷涌現(xiàn)出來(lái)。 7. As mentioned previously, these applications have tended to open up more slowly than originally predicted, as cost w

56、as really not much of a consideration in telecommunications, where equipment costs are swamped by other considerations. 如前所述，（線路）成本并非電信系統(tǒng)中真正重要的考慮因素，通信設(shè)備的成本主要受到其他因素的制約，因此這些應(yīng)用比預(yù)料的出現(xiàn)得慢。 8. As wavelengths decrease to approach the size of circuit components, circuit elements are no longer lumped as suc

57、h, and leads can act as reflective components and/or antennas and lumped elements as electromagnetic resonators. 隨著波長(zhǎng)減小到接近于電路元件的尺寸，電路單元就不再是集總的，導(dǎo)線可起到反射元件以及（或）天線的作用，集總單元?jiǎng)t成為電磁諧振器。 UNIT 10 1.The principles which underlie almost all digital audio applications and devices, be they digital synthesis, sa

58、mpling, digital recording or CD or iPod playback, are based on the basic concepts which follow in this chapter. New forms of playback, file formats, compression and storage of data are all changing on a seemingly daily basis, but the underlying mechanisms for converting real-world sound into digital

59、 values, manipulating those data and finally converting them back into real-world sound has not varied much since Max Mathews developed MUSIC I in 1957 at Bell Labs. 所有的數(shù)字音頻應(yīng)用程序和設(shè)備是在數(shù)字合成、采樣、數(shù)字錄音或CD或iPod播放的基礎(chǔ)上，都是基于最基本的概念,遵循在這一章的原則。新形式的播放,文件格式,壓縮和存儲(chǔ)的數(shù)據(jù)都在一個(gè)看似每天改變，但是這種聯(lián)系的潛在機(jī)制轉(zhuǎn)換為現(xiàn)實(shí)世界的聲音轉(zhuǎn)化為數(shù)字值,操縱這些數(shù)據(jù),最后將

60、他們轉(zhuǎn)化成真實(shí)世界的聲音沒(méi)有變化多少，因?yàn)轳R克斯馬修斯在貝爾實(shí)驗(yàn)室于開(kāi)發(fā)了音樂(lè)于20世紀(jì)60年代。 2.Sound is created by vibrations, such as those produced by a guitar string, vocal cords or a speaker cone. These vibrations move the air molecules near them, forcing molecules together, as a result raising the air pressure slightly. The air molecul

61、es that are under pressure then push on air molecules surrounding them, which push on the next set of air molecules, and so forth, causing a wave of high pressure to move through the air; as high pressure waves move through the air, they leave low pressure areas behind them. When these pressure lows

62、 and highs – or waves – reach us, they vibrate the receptors in our ears, and we hear the vibrations as sound. 聲音是由振動(dòng)產(chǎn)生的,如制作的吉他弦,聲帶或揚(yáng)聲器錐。這些振動(dòng)移動(dòng)附近的空氣分子，使分子連接在一起，因此提高空氣壓力略。這是在壓力下將空氣分子周圍的空氣分子，從而推動(dòng)下一組空氣分子等等,導(dǎo)致一波高壓進(jìn)入空氣; 高壓力波通過(guò)空氣移動(dòng),他們身后留下低壓區(qū)域。當(dāng)這些壓力低點(diǎn)和高點(diǎn)——或波動(dòng)——到達(dá)我們,他們?cè)谖覀兊亩湔駝?dòng)接收,我們聽(tīng)到時(shí)發(fā)出的震動(dòng)聲。 3.Unlike anal

63、og storage media such as magnetic tape and vinyl records, computers store audio information digitally as a series of zeros and ones. In digital storage, the original waveform is broken up into individual samples. This is know as digitizing or sampling the audio, and is sometimes called analog-to-dig

64、ital conversion. The sampling rate defines how often a sample is taken. For example, CD-quality sound has 44.100 samples for each second of a waveform. 不像模擬存儲(chǔ)媒體如磁帶和唱片,計(jì)算機(jī)存儲(chǔ)音頻信息數(shù)字化是一系列由0和1組成。在數(shù)字存儲(chǔ),原始波形分解成單獨(dú)的采樣。眾所周知作為數(shù)字化或抽樣音頻,有時(shí)被稱為模擬數(shù)字轉(zhuǎn)換。采樣率定義頻率取樣時(shí)。例如,cd品質(zhì)的聲音有每秒鐘44.100采樣波形。 4.The higher the sampling

65、 rate, the closer the shape of the digital waveform will be to the original analog waveform. Low sampling rates limit the range of frequencies that can be recorded, which can result in a recording that poorly represents the original sound. 采樣率越高，數(shù)字波形的形狀越接近原來(lái)的模擬波形。低采樣率限制頻率的記錄范圍，從而導(dǎo)致記錄不充分，難以表示原始的聲音。

66、 5.The sampling rate limit the frequency range of the audio file; to reproduce a given frequency, the sampling rate must be at least twice that frequency. For example, if the audio contains audible frequencies as high as 8,000 Hz, your need a sample rate of 16,000 samples per second to reproduce this audio accurately in digital form. This calculation comes from the Nyquist Theorem, and the highest frequency that can be reproduced by a given sample rate is known as the Nyquist Frequency. CDs h