Final answer:
Articulation clarity is the most helpful in differentiating between hypernasality and hyponasality, as it reflects the impact of nasal airflow on speech sounds.
Step-by-step explanation:
The most helpful aspect in differentiating between hypernasality and hyponasality is articulation clarity. Hypernasality refers to excessive nasal resonance during speech, often because the velopharyngeal closure does not fully prevent air from escaping through the nose. In contrast, hyponasality indicates a lack of normal nasal resonance, often due to a blockage in the nasal passages. Articulation clarity can help differentiate between these two conditions because hypernasal speech may make consonants sound less clear as air escapes through the nose, whereas hyponasal speech might result in more nasal sounds being perceived as muffled or less resonant due to nasal blockage. Pitch, volume, and rate of speech are less indicative of nasality issues and not as helpful in differentiation.