Natural language is vocally transmitted by speakers as speech sounds, and auditorily received by listeners as speech waves.

This can be contrasted with written language which is visually transmitted as physical markings, and interpreted as a script.

聲樂頻道是查爾斯·F·霍克特（Charles F. Hockett）提出的13個設計功能中的第一個，用於描述人類語言的特徵並將其與動物交流區分開來。
它描述了可使用語音信號產生語言的方式。說話者使用聲道來產生語音，而聽眾則使用聽覺設備來接收和處理語音

https://blogs.ntu.edu.sg/hg3040-2014-1/?page_id=54

https://en.wikipedia.org/wiki/Vocal-Auditory_Channe...

Vocal-Auditory Channel

Vocal-auditory channel is the first of 13 design features proposed by Charles F. Hockett in characterizing human language and distinguishing it from animal communication. It describes the way vocal signals can be used to produce language. The speaker uses a vocal tract (containing most of the speech organs) to produce speech sounds, and the hearer employs an auditory apparatus (the sense of hearing) to receive and process the speech sounds. This is why human language is said to be based on speech sounds produced by the articulatory system and received through the auditory system. The ...

Vocal-auditory channel is the first of 13 design features proposed by Charles F. Hockett in characterizing human language and distinguishing it from animal communication. It describes the way vocal signals can be used to produce language. The speaker uses a vocal tract (containing most of the speech organs) to produce speech sounds, and the hearer employs an auditory apparatus (the sense of hearing) to receive and process the speech sounds. This is why human language is said to be based on speech sounds produced by the articulatory system and received through the auditory system. The vocal channel is a particularly excellent means through which speech sounds can be accompanied or substituted by gestures, facial expressions, body movement, and way of dressing. However, Hockett considers this design feature one which is fundamentally advantageous for primates as "it leaves much of the body free for other activities that can be carried on at the same time."

from維基百科

重點在最後一句~!

天哪~~~

所以手腳空出來可以做手勢、臉部表情...

以下資料參考自 https://en.wikipedia.org/wiki/Hockett%27s_design_features

(A) Total Feedback 
Speakers of a language can hear their own speech and can control and modify what they are saying as they say it. Similarly, signers see, feel, and control their signing.

(B) Vocal-auditory channel
Refers to the idea that speaking/hearing is the mode humans use for language. When Hockett first defined this feature, it did not take sign language into account, which reflects the ideology of orality that was prevalent during the time.

(C) Displacement 易時易位性
Displacement refers to the idea that humans can...

以下資料參考自 https://en.wikipedia.org/wiki/Hockett%27s_design_features

(A) Total Feedback 
Speakers of a language can hear their own speech and can control and modify what they are saying as they say it. Similarly, signers see, feel, and control their signing.

(B) Vocal-auditory channel
Refers to the idea that speaking/hearing is the mode humans use for language. When Hockett first defined this feature, it did not take sign language into account, which reflects the ideology of orality that was prevalent during the time.

(C) Displacement 易時易位性
Displacement refers to the idea that humans can talk about things that are not physically present or that do not even exist. Speakers can talk about the past and the future, and can express hopes and dreams. A human's speech is not limited to here and now. 

(D) Productivity 能產性
Productivity refers to the idea that language-users can create and understand novel utterances. Humans are able to produce an unlimited amount of utterances.

四個選項都是Hockett's Design Feature 針對Human Language 所提出的Feature
只是符合Vocal-auditory的好處是選項(B)的描述