In the experimental phase of application of a new Non-Doppler technology (MEM system, Acoustic Imaging, Phoenix; Dornier Medizintechnik) we observed, that in patients, who spoke during colour imaging of a breast tumour, artifacts appeared in or around the lesion: the colour artifacts were seen regularly inside the tumour in cases of malignancies, and exactly surrounding benign tumours. Postoperative histological findings served as an objective criterion of classification/differentiation. To examine this phenomenon, we performed a study in 71 patients. These women with a sonographically detectable tumour (37 malignant, 34 benign) were examined on the day before surgery. We observed, that if patients uttered the number "99" with a relatively low voice or alternatively hummed a deep sound, the artifacts could be regularly visualized. In 66/71 patients (93%) status evaluation by artifact generation due to vocal fremitus examination was correct. In 3 patients the tumour was erroneously described as malignant, histology showing a proliferative mastopathy. In 2 cases the tumour was classified as benign, whereas histology revealed a malignancy, in both patients a large ductal-invasive carcinoma (> 3 cm). This phenomena could, however, not be reproduced with other colour techniques. A possible explanation is: Thoracic vibrations during speech can be registered by the MEM technique. These vibrations are not perpetuated into the benign lesion characterised by a displacing growth, due to which the vibrations are "barred off" at the borders of the tumour. Infiltrating growth typical of a malignancy causes transmission of these vibrations into the center of the tumour.(ABSTRACT TRUNCATED AT 250 WORDS)