This paper describes listening tests investigating the perceptual role of voice source parameters (other than FO) in signaling focal prominence. Synthesized stimuli were constructed on the basis of an inverse filtered utterance 'We were away a year ago'. Voice source parameters were manipulated in the two potentially accentable syllables WAY and YEAR (in terms of the absolute magnitude and alignment of peaks) and to provide source deaccentuation of post-focal material. Participants in the first listening test were asked to decide whether the syllable WAY, YEAR or neither was deemed the most prominent: judgments on the degree of prominence and naturalness were also indicated on a continuous visual analogue scale. In the second test listeners indicated the degree of prominence for every syllable in the phrase. For WAY, voice source manipulations can cue focal accentuation, and both the magnitude of the source manipulation of the syllable and the presence of source deaccentuation contribute to the effect. However, for YEAR, listeners' perception of focal accentuation tended to show relatively minor increases in perceived prominence regardless of the source manipulations involved. It therefore appears that the source expression of focus is sensitive to the location of focus in the intonational phrase.