Subjective Tones

主观音调

When two single-frequency tones are present in the air at the same time, they will interfere with each other and produce a beat frequency. The beat frequency is equal to the difference between the frequencies of the two tones and if it is in the mid-frequency region, the human ear will perceive it as a third tone, called a "subjective tone" or "difference tone". The difference tones are always present, but they can be made prominent by using two high, clear tones like the notes of a flute. With two flutes you can produce a "trio for two flutes". This phenomenon can also be produced with one brass instrument (multiphonics). If a French horn player plays one note and hums another, then the subjective tone which is the difference between them can sometimes be heard clearly.

当两种单频声音同时存在于空气中时，它们会相互干扰并产生拍频。拍频等于两种声音频率之差。如果该拍频位于中频区域，人耳会将其感知为一个第三声音，称为‘主观音’或‘差音’。差音始终存在，但可以通过使用两个高而清晰的声音（如 flute 的音符）使其更加突出。使用两把 flute 可以产生一种称为‘两 flute 三重奏’的现象。这种现象也可以通过一把铜管乐器（multiphonics）产生。如果法国号演奏者演奏一个音符并同时哼唱另一个音符，那么这两个音之间的主观音有时可以被清晰地听到。

One important role of subjective tones is the missing fundamental effect whereby a correct sense of pitch for a musical sound may be maintained even if the poor fidelity of the sound reproduction has filtered out some of its lower harmonics.

主观音调的一个重要作用是缺失基音效应，即即使声音再现的保真度较差，滤除了某些低次谐波，仍能保持对音乐声音音调的正确感知。

Missing Fundamental Effect

缺失的基本效应

The subjective tones which are produced by the beating of the various harmonics of the sound of a musical instrument help to reinforce the pitch of the fundamental frequency. Most musical instruments produce a fundamental frequency plus several higher tones which are whole-number multiples of the fundamental. The beat frequencies between the successive harmonics constitute subjective tones which are at the same frequency as the fundamental and therefore reinforce the sense of pitch of the fundamental note being played.

If the lower harmonics are not produced because of the poor fidelity or filtering of the sound reproduction equipment, you still hear the tone as having the pitch of the non-existant fundamental because of the presence of these beat frequencies. This is called the missing fundamental effect. It plays an important role in sound reproduction by preserving the sense of pitch (including the perception of melody) when reproduced sound loses some of its lower frequencies.

如果由于声音再现设备的保真度或滤波性能不佳而没有产生低次谐波，你仍然会因为这些拍频的存在而感知到不存在的基频的音调。这种现象称为缺失基频效应。它在声音再现中起着重要作用，尤其是在声音失真一些低频成分时，仍能保持音调感（包括旋律感知）。

The presence of the beat frequencies between the harmonics gives a strong sense of pitch for instruments such as the brass and woodwind instruments. For percussion instruments such as the cymbal, the sense of pitch is less definite because there are non-harmonic overtones present in the sound.

谐波之间的拍频现象使 brass 和 woodwind 乐器具有明确的音调感。而对于如 cymbal 这样的打击乐器，由于声音中存在非谐波泛音，其音调感则不够明确。

由乐器声音的各种谐波的拍击所产生的主观音调有助于加强基频的音调感。大多数乐器产生的声音包括基频以及几个更高频率的音调，这些音调是基频的整数倍。 successive harmonics 之间的拍频构成了与基频频率相同的主观音调，因此加强了正在演奏的基频音调的感觉。

Multiphonics

多音现象

One of the applications of subjective tones is the production of three tones by a single brass player. The player plays a note in the usual way but in addition hums a second note into the mouthpiece. The beat frequency between these two notes produces a third tone. Such tones are sometimes called multiphonics.

主观音调的一个应用是用一个铜管乐手产生三个音调。乐手通常方式演奏一个音符，同时还将另一个音符哼入嘴孔。这两个音符之间的拍音产生第三个音调。这种音调有时被称为多音调。