频率转音符计算器

常见问题

频率到音符计算器是如何工作的？

该计算器使用公式 n = 12 × log₂(f/440) 将频率（Hz）转换为 MIDI 音符编号，然后映射到对应的音符名称（如 A4、C#5）。其中 440 Hz 是标准音 A4 的频率。

什么是标准音高 A440？

A440（即 440 Hz）是国际标准音高，规定 A4 音符的频率为 440 Hz。这是全球管弦乐团和调音设备的基准频率，尽管部分乐团使用 A441 或 A442 进行调音。

音符频率是如何计算的？

在十二平均律中，每个八度有 12 个半音，频率每升高一个八度翻倍。从 A4（440 Hz）开始，每升高一个半音频率乘以 2^(1/12) ≈ 1.0595。例如，A5 = 880 Hz，A3 = 220 Hz。

音分（cents）是什么？

音分是比半音更小的音高单位，1 个半音 = 100 音分。音分用于表示音高的微小偏差，例如 +15 音分表示比标准音高偏高 15/100 个半音。调音器和音频处理软件常用音分来显示偏差。

How Frequency to Note Conversion Works

In equal temperament, notes are spaced so that each semitone is a fixed frequency ratio of 2^(1/12) ≈ 1.0595. The reference pitch is A4 = 440 Hz. Given any frequency, we calculate its distance from A4 in semitones, round to the nearest semitone, and look up the note name.

semitones from A4 = 12 × log₂(freq / 440)

MIDI note = round(semitones) + 69

cents deviation = 1200 × log₂(freq / nearest_note_freq)

Note Frequency Reference Table

Note	Hz	MIDI
C4 (Middle C)	261.63	60
D4	293.66	62
E4	329.63	64
F4	349.23	65
G4	392.00	67
A4 (Concert A)	440.00	69
B4	493.88	71
C5	523.25	72
A3	220.00	57
A5	880.00	81

What Are Cents?

Cents are a logarithmic unit for measuring intervals between pitches. One semitone = 100 cents. A perfectly in-tune note has 0 cents deviation. Most human ears can detect deviations of about 5–10 cents. ±50 cents is the maximum deviation before a note is considered the next semitone.

0 cents — perfectly in tune
±5 cents — barely perceptible to most ears
±10 cents — most listeners notice slight out-of-tuneness
±25 cents — clearly out of tune
±50 cents — exactly between two notes

Related Tools

Delay Time Calculator — BPM to milliseconds for all note values
Wave Frequency Calculator — v = f × λ for sound and light waves

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