What characterizes a nasal sound?

A nasal sound is characterized by the airflow being directed through the nose rather than the mouth. This type of sound is produced when the velum, a part of the roof of the mouth, lowers, allowing air to escape through the nasal passages while the mouth is either closed or partially open. English phonemes such as /m/, /n/, and the nasal sound in "sing" (/ŋ/) are examples of nasal sounds, which distinctly demonstrate this airflow pattern.

The other characteristics do not apply to nasal sounds. For instance, in typical speech production, air is not only forced through the mouth for all sounds; many sounds are articulated with airflow through both the mouth and nose in the case of nasals. Additionally, the production of nasal sounds does involve vocal cord vibration, as they are voiced sounds. Lip movement can occur for various phonetic sounds, but it is not a defining characteristic of nasality itself. The key feature of nasal sounds is the directed airflow through the nose, making the correct answer clear.