Towards the influence of vibration on evaluation of speech utterances in mobile devices

In this paper the influence of vibrotactile stimuli on the evaluation of loudness of speech is investigated. The speech utterances consisted of context-free consonant-vowel-consonant (CVC) and vowel-consonant-vowel (VCV) utterances played over headphones on a mobile phone. The phone´s standard vibration was used as the tactile stimulus. Using an AB/X paradigm, 32 untrained subjects evaluated loudness differences with and without vibration for 50 different speech signals. The speech signals were played in 8 steps of loudness differences distributed around just noticeable difference. A significant increase of error in loudness evaluation was found for moderate differences in loudness when tactile stimuli were presented with a speech sample. Further statistical analysis also indicated a significant subjective influence.