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Overview to Part I

The 采样 nothing more than a numberis the atom of 声波 理论 says that we can construct any 声波 emitted by a 扬声器 by 中项 of a 系列 of 采样 that trace the 模式 of a 声波 波形 over 时间 But 理论 becomes 现实 only when strict 技术 conditions concerning 采样 率 and 采样 width are met

The first chapter by John Strawn and 柯蒂斯 罗兹 涵盖 such 基础 topics as the 历史 of 数字 錄/录 the 采样 theorem aliasing 相位 correction 量化 抖动 為耳/音频 converters 过采样 and 数字 為耳/音频 格式

背景

* 历史 of 数字 為耳/音频 Recording

声波 錄/录 has a rich 历史 beginning with Thomas 爱迪生 and Emile Berliner's experiments in the 1870s and marked by V Poulsen's Telegraphone 磁 wire 錄機/录机 of 1898 Read and Welch 1976

Although the invention of the triode vacuum tube in 1906 launched the era of 电子 电子 产生 records did 不 become practical until 1924 Keller 1981

Optical 声波 錄/录 on 电影 was first demonstrated in 1922 Ristow 1993 声波 錄/录 on 磁带 coated with powdered magnetized 材料 was 发展 in the 1930s in Germany figure 1 3 but did 不 reach the rest of the world until after World War 2

* 实验 数字 Recording

The core 概念 in 数字 為耳/音频 錄/录 is 采样 that is 转换 continuous 模拟 信号 such as those coming from a 声筒（麦克风） into 离散 time-sampled 信号 The 理论 underpinning of 采样 is the 采样 theorem which specifies the 关系 between the 采样 率 and the 為耳/音频 频带宽度（带宽） see the section on the 采样 theorem later in this chapter This theorem is also called the 尼奎斯特 theorem after the 作品 of 哈罗德 尼奎斯特 of Bell Telephone Laboratories 尼奎斯特 1928 The British researcher A Reeves 发展 the first patented 脉冲编码调制 脉冲编码调制（脉码调制） 系统 for 传送 of 信息 in 振幅对分/对仗 时量 数字 形（曲）式 Reeves 1938 Licklider 1950 Black 1953

In the late 1950s Max Mathews and his group at Bell Telephone Laboratories 生成 the first synthetic 声 from a 数字 算機/计算机 The 采样 were written by the 算機/计算机 to expensive and bulky reel-to-reel 算機/计算机 磁带 storage drives

By 1977 the first 商业 錄/录 系统 came to market the Sony PCM-1 处理器 designed to encode 13-bit 数字 為耳/音频 信号 onto Sony Beta format videocassette 录机 Within a year this was displaced by 16-bit 脉冲编码调制（脉码调制） encoders such as the Sony PCM-1600 Nakajima et al 1978 The professional Sony PCM-1610 and 1630 became the 标准 for compact 碟盘 CD 掌控（母带处理） These 标准 continued throughout the 1980s

* 数字 声波 for the Public

数字 声波 first reached the 一般 大众 in 1982 by 中项 of the compact 碟盘 CD format a 12-cm optical 碟盘 read by a laser figure 1 5

* 数字 声波 for Musicians

Although CD players had inexpensive 16-bit DACs good-quality converters attached to 算機/计算机 were 不 common before 1988 Only in the late 1980s did low-cost good-quality converters become available for personal 算機/计算机 In a short period 声波 合成 錄/录 and 处理 by 算機/计算机 became widespread Dozens of different 為耳/音频 工作站 reached the 樂/乐 marketplace

* 数字 多轨 Recording
In 对比 to 立体声 录机 that 录 both left and right 通道 at the same 时间 多轨 录机 have 几个 离散 通道 or 轨道 that can be 录制 at different times Each 轨 can 录 a separate 乐器 for 例如 allowing flexibility when the 轨道 are later 混

The first 算機/计算机 盘载体 随机存取 声波 editor and mixer was 发展 by the Soundstream company in Salt Lake City Utah see figure 16 38 Their 系统 allowed 混 of up to eight 轨道 or 声波 files 储存 on 算機/计算机 光盘/磁盘 at a 时间 Ingebretsen and Stockham 1984

For a 数 of years 数字 多轨 錄/录 was a very expensive enterprise figure 1 7 The situation entered a new 相位 in the early 1990s with the introduction of low-cost 多轨 磁带 录机 by Alesis and Tascam and inexpensive 多轨 光盘/磁盘 录机 by a variety of concerns