Child-Directed Speech in Noise: Testing Signal- and Code-Based Phonetic Enhancement

Area of Science:

• Speech and Language Pathology
• Developmental Psychology
• Acoustic Phonetics

Background:

• Talkers naturally adjust speech based on listener needs and context.
• Child-directed speech (CDS) may enhance intelligibility and support language development.

Purpose of the Study:

• To investigate how mothers adapt child-directed speech (CDS).
• To examine if adaptations serve immediate intelligibility or long-term language development goals.

Main Methods:

• 28 mothers interacted with their 3-5 year old children or an adult.
• Speech was recorded in low and high background noise (56 vs. 75 dB SPL).
• Acoustic-phonetic analyses compared CDS and adult-directed speech (ADS).

Main Results:

• Mothers significantly increased pitch, pitch variability, and intensity in CDS, especially in noise and for younger children.
• CDS exhibited a higher signal-to-noise ratio than ADS.
• Limited phonetic enhancement of segmental features was observed; vowel category separation decreased.

Conclusions:

• Mothers enhance suprasegmental speech properties in CDS but not phonetic (segmental) properties.
• No evidence of phonetic enhancement in preschool children's CDS during noisy dyadic communication was found.