hellog〜英語史ブログ / 2022-02-19

■ #4681. 言語音の周波数とピッチの関係 [phonetics][acoustics][stress][intonation][prosody]

　言語音にはピッチ (pitch) という属性がある．高い声の人，低い声の人もいれば，同じ人でも高い声で話すとき，低い声で話すときがある．話者個人の問題というよりも，言語的な特徴としてのピッチもある．抑揚 (intonation)，高低アクセント (pitch accent)，声調 (tone) などがそれである．
　ピッチは周波数 (frequency) と関連が深い．両者は同一視されることも多いが，厳密にいえば周波数は音の高低に対応する物理的な指標であり，ピッチはそのような音の高低に対する心理的な指標である．前者は音響音声学的な指標，後者は聴覚音声学的な指標といってもよいだろう．この点について，言語学百科辞典の PITCH の項より2カ所ほど引用する．

When an object vibrates, its movement produces changes in air pressure that radiate like waves from the source. If the frequencies of the vibrations are roughly between 20 and 20,000 cycles per second, or Hertz (Hz), ideally they can be heard by a young, healthy human listener. The range of hearing frequencies declines with age. The physical characteristic of the vibrating body, frequency, produces a psychological experience called pitch. In general, a low frequency produces the sensation of a low pitch (for example, the 60 Hz hum produced by electrical power in a poorly grounded radio), with the pitch increasing as the frequency increases (a male voice at 100 Hz, a female voice at 200 Hz, a child's voice at 300 Hz). Because there is a close correspondence between frequency and pitch, people frequently use the terms interchangeably. However, in addition to frequency, the sensation of pitch is influenced by an interaction between the amplitude of the vibration and the range of the frequency. Pitch is also influenced by the complexity of the vibration and its corresponding wave form. (623)

Pitch is closely related to the physical stimulus frequency, but as a psychological event, it is influenced by the complexity, frequency range, and loudness of the tone. (624)

　要点は，音響装置が機械的に感知する言語音の高さ（周波数）と人間が感知する言語音の高さ（ピッチ）は，確かに密接な関係はあるもののイコールではないということだ．ピッチは，言語音の音響学的な要因のほかにも，他の様々な要因の影響を受けて決まる．関連して「#2687. 言語音の周波数と音圧レベル」 ([2016-09-04-1]) も参照．

　・ Hogan, Patrick Colm, ed. The Cambridge Encylopedia of the Language Sciences. Cambridge :CUP, 2011.

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