The most noticeable trend in information technology from a system perspective has been the increasing integration of media. Traditionally， computer systems dealt exclusively with numerical calculations. However， text processing soon became an important concern for computer designers. Communication technologies were also developed to support the transmission of textual and numerical data. More recently， there has been a dramatic increase in the range of media types supported by computers and communications technologies. Significant steps have been taken in integrating graphics into computer workstations and communications technology. Researchers are now tackling the harder problems presented by audio and video.
【Vocabulary】
perspective
n. 远景，前途；透视图；看法，观点
cooperate
vi. 合作，协作
pressure
n. 压力，电压，强迫
dramatic
adj. 戏剧性的，生动的
initially
adv. 最初地，开头的
decentralization
n. 分散，排除集中
overload
vt. 使超载，超过负荷
volume
n. 体积，大量，音量
achieve
vt. 完成，达到
starvation
n. 饥饿，饿死
combination
n. 结合，合并，化合
infrastructure
n. 下部构造，基础下部组织
integration
n. 综合
textual
adj. 文本的，原文的
graphic
adj. 绘画的，图解的
tackling
n. 抱住，卷起
【参考译文】
信息技术的发展
要了解多媒体计算背后的动因，有必要从最终用户（相对于技术人员）角度考察一下信息技术。对于最终用户来讲，信息技术涉及的是能访问各种形式的信息并能通过这些各种形式的信息进行协作（共同完成任务）。任何一种有益于完成这一任务的实际技术在最终用户看来只不过是一种工具而已。
从这一角度来看，我们有可能把信息技术从两个不同的方面表达：最终用户可用的媒体形式和利用媒体方式进行有效通信的能力。现代信息用户在这两方面都面临着越来越大的压力。这些压力将在下面更为详细地讨论。
1．媒体形式
这些年来，用于传输信息的媒体范围增加了许多。最初，通信仅限于简单形式的媒体，如声音和纸张。但在20世纪，引入了大量的不同媒体类型，如电话和可视媒体。20世纪末，这种趋势在加剧。现阶段，可用于传输信息的媒体类型范围很广。
这方面的进展为教育和商业等相关领域提供了许多新的发展机会。但是，同时也出现了与社会信息激增有关的一系列问题，尤其是存在着很大的产生信息过量的危险。这个问题在商务活动中能够见到，例如，行政决策者们必须根据不断增加的各种各样的信息做出决策。类似的问题同样也出现在政府、医疗和教育部门等领域。
2．通信问题
从用户角度讲，信息技术更进一步的发展趋势是信息的分散化。现代的多数机构组织都非常庞大并且大多由若干个独立的分支机构构成。这些分支机构通常通过共享的交换信息而协同工作。这种情况下，通信对大多数机构来讲就非常关键。高效的通信能使成功与失败差距巨大。没有适合的通信形式，就存在着信息匮乏的危险，也就是说，决策者们没有恰当的信息用于正确的决策。
3．信息技术的需求
因此，最终用户面临着两个问题：信息过量和信息匮乏。他们要么拥有过多的信息，要么没有恰当的信息，因此需要帮助最终用户管理信息以便减轻由不断增加的信息重要性所产生的负担。本质上讲，最终用户需要的是在恰当的时间把恰当的信息提供给适当的人。显然这一点不能借助手工系统来完成，这样就必须使信息管理过程自动化。
从系统观点看，信息技术涉及的是信息的处理和在不同的位置进行信息通信的能力。更为特别的是，信息技术被认作是计算技术和通信基础的结合。这项技术的目标实质是为最终用户管理信息。
从系统角度看，信息技术最为显著的发展趋势就是不断地使媒体集成。传统上，计算机系统仅仅处理数值计算。但是，随后文本处理变为计算机设计者们一个非常关心的问题。通信技术也被开发成能够支持文本和数值数据的传输，近来，计算机和通信能够支持的媒体类型激增，有关把图形集成到计算机工作站和通信技术的工作已取得重要进展，研究人员正在着手解决由音频和视频所产生的更为棘手的问题。
【Reading Material】
The Physics of Sound
Sound is created by the vibration of an object. The object transmits its vibrations to the air surrounding it， creating waves of air pressure. These waves travel through the air to our eardrums. The eardrums transfer the vibration to our inner ear， which in turn sends signals to the brain， and we interpret the vibration as sound. This basic mechanism is the means by which all sounds are created and perceived； one object causes air to vibrate， and another object captures the vibration.
Frequency andAmplitude
Sound waves have two basic characteristics： the number of times the wave vibrates in a given period of time （called frequency） and the strength of the vibrations （called amplitude）.
Frequency is directly related to the pitch of a sound. High-pitched sounds are caused by rapid vibrations such as the piercing squeal of a whistle or a high note played on a violin.
Low-pitched sounds are caused by slower vibrations such as the rumble of a passing train or a low note played on a piano. We usually measure the frequency of sound in terms of vibrations per second. Sound engineers have adopted the scientific convention of hertz （abbreviated Hz）， or cycles per second， to describe the frequency of a sound. For example， a common tuning reference on a piano， the note A below middle C， is described as 440 Hz.
Amplitude corresponds to the volume of a sound. The greater distance between the top and the bottom of a sound wave， the greater the amplitude. A good way to visualize this is to think of a guitar string. If you touch the string gently， it vibrates at a fixed rate （in other words， at a fixed frequency）， but the distance between the top and bottom of the area in which it vibrates is small. Give the string a good， strong pluck， and the distance over which the string vibrates increases greatly. As a result， the string moves more air， and the volume is louder.b
Amplitude， or loudness， is described in decibels. A decibel is abbreviated as dB （i.e. one-tenth of a bell）， a sound pressure level measurement named after Alexander Graham Bell. We need to clarify the concept of decibels here， because you’ II encounter the decibel frequently in the audio world. The dB unit （dBu） is used to measure two related but very different phenomena. One is the sound pressure level （SPL）， the actual loudness perceived by your ears. This is based on the strength of air pressure changes caused by vibrations or “sound waves” traveling through the air. For purposes of comparison， the ambient background noise of a recording studio registers about 20 dB SPL， regular human speech at a distance of one foot registers 70 dB SPL， and a jet plane engine registers about 130 dB SPL.
The second use of the decibel is the measure of audio signal level as an electrical phenomenon. One real-world example is the strength of a line level voltage， frequently expressed as-10 dB. Another example is the dB meters you see on a tape recorder or mixer. In the real world， this is the important thing to remember： when dealing with decibels in terms of cables or connecting hard-ware， be sure the voltage levels match. When using decibel level as a measure of signal strength （as with volumes is a mixer）， it is useful for comparing the level of different signals. The values are expressed relative to 0 dB， the point at which the signal going out is the same strength as the signal coming in.
