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2的12次方根

2的12次方根
2的12次方根
數表无理数
- - - - - -
識別
種類無理數
符號
位數數列編號OEISA010774
性質
連分數[1; 16, 1, 4, 2, 7, 1, 1, 2, 2, 7, 4, 1, 2, 1, 60, 1, 3, 1, 2]
以此為的多項式或函數
表示方式
1.05946309...
二进制1.00001111001110001111100100101101
十进制1.05946309435929526456182529494634
十六进制1.0F38F92D97962CBCB533704A0D391B84

2的12次方根是一個代數無理數,計為,是方程式的正實根。它是音樂理論中的一個重要常數,它代表了十二平均律半音頻率比。

數值

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的近似值為1.0594630943593,其值略高於[1] ≈ 1.0588。更好的近似值為 ≈ 1.059459或 ≈ 1.0594630948。

性質

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  • 方程式的正實根
  • 超體積為2的12維超立方體之邊長
  • 其值約為1.0594630943593 (OEIS數列A010774
  • 連分數為:
    OEIS數列A103922

半音音階

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因為音程是頻率的比例,等於平均律半音音階劃分八度(具有2:1的比例)成12等份。

利用此比值,以半音音階的音調從最接近且高於中央C的A以頻率440開始,產生音高的順序與波的頻率如下:

音符
 
頻率
Hz
倍率
 
係數
(六處)
A 440.00 20/12 1.000000
A/B 466.16 21/12 1.059463
B 493.88 22/12 1.122462
C 523.25 23/12 1.189207
C/D 554.37 24/12 1.259921
D 587.33 25/12 1.334839
D/E 622.25 26/12 1.414213
E 659.26 27/12 1.498307
F 698.46 28/12 1.587401
F/G 739.99 29/12 1.681792
G 783.99 210/12 1.781797
G/A 830.61 211/12 1.887748
A 880.00 212/12 2.000000

最終的A(880 Hz)的頻率為初始的A(440 Hz)的兩倍,也就是說,他們差了八度。

間距調整

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由於一個半音的頻率比接近106%,一個錄音的播放速度增加或減慢6%將會使音高向上或向下一個半音移位“半步”。

參見

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參考文獻

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  1. ^ 卓仁祥《从文化角度看十二平均律的发现》美国TEXAS大学
  • Barbour, J.M.. A Sixteenth Century Approximation for Pi, The American Mathematical Monthly, Vol. 40, no. 2, 1933. Pp. 69–73.
  • Ellis, Alexander and Hermann Helmholtz. On the Sensations of Tone. Dover Publications, 1954. ISBN 0-486-60753-4
  • Partch, Harry. Genesis of a Music. Da Capo Press, 1974. ISBN 0-306-80106-X
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2的12次方根
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