Clear speaking styles have been demonstrated to enhance certain acoustic-phonetic features of speech. However, previous work on speech production changes has mainly used interactions with imaginary interlocutors or read speech. In this study, two types of altered speech modes were elicited through a new combination of ‘gap’ and ‘map’ tasks, which leads to unscripted dialogues between interlocutors. British speakers completed a task in cooperation with an adult native speaker or adult foreigner, in quiet and in noisy conditions. Speaker productions were analyzed to examine changes related to vowel and consonant duration in voiced and voiceless rhymes in naturally elicited speech in adverse conditions. Vowel shortening in voiceless contexts was present. The durational contrast between voiced and voiceless rhymes was reduced in altered speech styles for vowels and maintained for plosives.