# 位元深度 (音訊)

## 二進位表示

PCM訊號是一段數位音訊取樣值序列，它所包含的資料可為原始類比訊號提供必要資訊。在序列中，所有取樣值在時間上間隔均勻，各自代表訊號在對應時間點上的振幅。振幅是每個取樣點所精確儲存的唯一資訊，其儲存形式通常是整數浮點數形式，但會編碼成具有固定位數的二進位數。該二進位數之位數就是取樣的位元深度（英語：bit depth），也稱作字長（英語：word length）或者字大小（英語：word size）。

## 量化

${\displaystyle \mathrm {SQNR} =20\log _{10}(2^{Q})\approx 6.02\cdot {}Q\ \mathrm {dB} }$

4 24.08 dB 16 −8至+7
8 48.16 dB 256 −128至+127
11 66.22 dB 2,048 −1,024至+1,023
12 72.24 dB 4,096 −2,048至+2,047
16 96.33 dB 65,536 −32,768至+32,767
18 108.37 dB 262,144 −131,072至+131,071
20 120.41 dB 1,048,576 −524,288至+524,287
24 144.49 dB 16,777,216 −8,388,608至+8,388,607
32 192.66 dB 4,294,967,296 −2,147,483,648至+2,147,483,647
48 288.99 dB 281,474,976,710,656 −140,737,488,355,328至+140,737,488,355,327
64 385.32 dB 18,446,744,073,709,551,616 −9,223,372,036,854,775,808至+9,223,372,036,854,775,807

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