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音高移位

In an inexpensive 采样器 it may 不 be 可能 to store every 音符 played by an acoustic 乐器 These samplers store only every third or fourth semitone and obtain 中级 音符 by 移位/偏移 the 音高 of a nearby 储存 音符 If you 录 a 声波 into a 采样器 内存（记忆） and play it back by pressing different keys the 采样器 carries out the same 音高移位 技能 A side 效果（效应） of simple 音高 移位/偏移 is that the sound's 时值 增 or 减 depending on the key pressed

Two 方法 of simple 音高 移位/偏移 存在 Both of these 方法 are called 时域 技术 since they operate directly on the 时域 波形 This is different from the 频域 音高移位 技术 discussed

音高移位 by 采样率 转换 with a 持续 回放 采样 频率 Top If every other 采样 is skipped on 回放 the 信号 is decimated and the 音高 is 移位/偏移 up an 倍频程（八度） Bottom If twice the 数 of 采样 are used by 中项 of interpolation on 回放 the 信号 is 移位/偏移 down an 倍频程（八度）


采样率 转换 Without 音高移位

Many 数字 為耳/音频 录机 operate at the 标准 采样 rates of 48 or 44 1 KHz How can we resample a 錄/录 at one of these 频率 so as to play it back at the other 频率 with no 音高 shift?To convert a 信号 between the 标准 采样 rates of 44 1 and 48 KHz without a 音高 change a rather elaborate 转换 过程 is required

These 比率 can be implemented as six stages of interpolations and decimations by 因素 of 2 3 5 and 7

1 Interpolate by 4 from 44 100 to 176 400 赫兹（he zi）
2 Decimate by 3 from 176 400 to 58 800 赫兹（he zi）
3 Interpolate by 4 from 58 800 to 235 200 赫兹（he zi）
4 Decimate by 7 from 235 200 to 33 600 赫兹（he zi）
5 Interpolate by 10 from 33 600 to 336 000 赫兹（he zi）
6 Decimate by 7 from 336 000 to 48 000 赫兹（he zi）

The 信号 can then be played back at a 采样 率 of 48 KHz with no change of 音高