Fundamental Frequency

The lowest frequency of a periodic sound wave, corresponding to the rate at which the vocal folds vibrate during voiced speech. Fundamental frequency (F0) is perceived by listeners as pitch and is a primary component of prosody — the rhythm, stress, and intonation of speech. F0 varies with speaker characteristics (typically 85-180 Hz for adult males, 165-255 Hz for adult females) and is modulated during speech to convey emphasis, emotion, and grammatical structure such as questions versus statements. Research has shown that individuals with autism spectrum disorder and Down syndrome may exhibit atypical F0 patterns, including restricted pitch range or inappropriate pitch variation, which can affect speech intelligibility and social communication.