What defines fricatives in terms of sound production?

Fricatives are defined specifically by the manner in which they are produced, which involves forcing air through a narrow channel created by two articulators in the vocal tract. This constriction creates a turbulent airflow, leading to the characteristic continuous sound associated with fricatives.

In this context, the defining element is the creation of sound through the compression of the air stream, which distinguishes fricatives from other types of speech sounds. By allowing air to flow through a small opening, voiced or voiceless characteristics can emerge, but the key feature is the turbulence generated from that constriction.

Other answer options may mention aspects of sound production, such as voicing or specific articulatory features, but they do not capture the fundamental principle that defines fricatives, which hinges on the mechanism of airflow and constriction.