信息科学与电子工程专业英语.doc

UNIT 10 The principles which underlie almost all digital audio applications and devices, be they digital synthesis, sampling, 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 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. 所有的数字音频应用程序和设备数字合成、采样、数字录音或CD或iPod播放都是基于最基本的概念,遵循在这一章新形式的播放,文件格式,压缩和存储的数据都在一个看似每天改变但是这种联系的潜在机制转换为现实世界的声音转化为数字值,操纵这些数据,最后将他们世界的声音没有变化多少因为马克斯·马修斯在贝尔实验室音乐– or waves – reach us, they vibrate the receptors in our ears, and we hear the vibrations as sound. 声音是由振动,如制作的吉他弦,声带或扬声器锥。这些振动移动附近的空气分子，使分子连接在一起，因此提高空气压力略这是在压力下将空气分子周围的空气分子，推动下一组空气分子等等,导致一波高压进入空气; 高压力波通过空气移动,他们身后留下低压区域。当这些压力低点和高点——或波——到达我们,他们在我们的耳朵振动,我们听到时发出的震动声。不像模拟存储媒体如磁带和唱片,计算机存储音频信息数字化是一系列由0和1组成。在数字存储,原始波形分解成单独的。作为数字化或抽样音频,有时被称为模拟数字转换。采样率定义频率取样时。例如,cd品质的声音每秒钟44.100波形。采样率越高，数字波形的形状越接近原来的模拟。低采样率限制频率，从而导致记录，原始的声音。采样率限制的音频文件的频率范围复制一个给定的频率，采样率必须至少两倍的频率。例如,如果音频包含声音频率高达8000赫兹, 你需要一个采样率为每秒16000个样本复制本音频准确数字形式。这个计算来自于奈奎斯特定理,和最高的频率可以复制出一个给定的采样率是众所周知的奈奎斯特频率。cd有一个采样率的每秒44100个样本,允许样本22050赫兹,这是高于人类听觉的极限,20000赫兹。Uint 11 They are transmitting high-resolution full color images at the rate of 30 images per second, a transfer speed that enables full size full quality image viewing in real time. 他们在30帧每秒的速率传输高分辨率全彩色图像，传输速度全尺寸的完整的图像质量实时查看。An image is a 2-dimensional distribution of energy, typically of visible electromagnetic radiation (light) but can also be of x-rays, ultraviolet, infrared or other radiation: electrons, acoustic waves or even nuclear particles. 图像是一个能量的二维分布，通常可见的电磁辐射（光）也可以是X射线，紫外线，红外线或其它辐射：电子，声波甚至核粒子。High resolution and full color are important for such examinations of standard prepared specimens, but resolution and colors may be reduced for f