This research investigates whether properties of speech to infants constitute hyperspeech modifications, as defined by Lindblom’s H&H Theory. Past research has presented infant-directed (ID) speech as an accommodative style whose acoustic features provide babies with structured input for making sense of speech and acquiring mappings between sound and meaning. However, with most investigations focused on effects of this style on infants' perceptual abilities, little quantitative information is available for the ID speech signal itself. By comparing ID speech with other listener-oriented styles (i.e. computer-directed speech, 'foreigner talk', and Lombard speech), the author seeks to address the following questions: (1) do different listener constraints elicit characteristic forms of modulation by speakers?, and (2) how does ID speech compare with other accommodative styles in the use of hyperspeech features? Fundamental frequency, intensity, the 1st and 2nd formants, segment duration, and speech rate are among the acoustic parameters analysed in this investigation.