Sound source of voiced fricatives

[Shijie Yao]

For voiceless fricatives such as [s] and [f], the sound source is definitely the turbulent airflow. But what about voiced fricatives?
One certain sound source is the vocal folds as their vibration results in voicing. Can I say the turbulent airflow is also one possible sound source of voiced fricatives?

I failed to find reliable references on the Internet. So some clarification would be greatly appreciated.

Thanks in advance!

[Simon]

Voiced fricatives have two sound sources. The clue is in the name:

voiced = the vocal folds are vibrating.

fricative = there is turbulent airflow caused by a constriction somewhere in the vocal tract.

If we want to synthesise such a sound using a vocoder, we will need what is called “mixed excitation“, in other words, a mixture of periodic and aperiodic sources. Some very simple vocoders cannot do this, because they switch between the two sources and can’t mix them together.

[Shijie Yao]

That’s very clear explanation. Thank you!

And a follow-up question. If it’s true to say “the turbulent air is one of the sound source of voiced fricatives”, then is it also acceptable to say “a constriction somewhere in the vocal tract is one of the sound source of voiced fricatives”?

Personally I found the alternative wording a wee bit strange but still acceptable…

(Well actually this exam question has been torturing me for some days…

[Simon]

It’s fine to say that a constriction in the vocal tract is a source of sound, in the same way that we say the vocal folds are a source of sound.

Neither of these parts of the anatomy actually creates sound itself. They do so by changing the airflow. The vocal folds interrupt the airflow periodically. A constriction (if narrow enough) will create turbulent airflow.

If we were being super-strict with the wording, perhaps we might say that these are the locations of sound sources.

[Shijie Yao]

I see, thanks again!

Have a nice working Christmas in Japan! メリークリスマス(Merry Christmas)！

[Author]

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