What is an important feature of fricatives?

Fricatives are characterized by the production of turbulent airflow through a narrow constriction in the vocal tract. This turbulence is what distinguishes fricatives from other consonant types, such as stops, which involve complete closure followed by a release. The sound is produced continuously as the air is forced through the narrow gap, creating a hissing or buzzing quality. This turbulent airflow is critical for the identification and classification of fricative sounds in phonetics.

The other options do not accurately reflect the defining characteristics of fricatives. For instance, while some fricatives can be voiced, not all are; thereby, they cannot be exclusively classified as voiced. Additionally, fricatives do not produce a harmonic tone, as this feature is more associated with voiced sounds in general, or specific tonal languages. Lastly, the occurrence of fricatives at the end of words is not a defining feature, as they can appear in various positions within a word or syllable structure. Thus, the key defining characteristic is indeed the turbulence created in the airflow.