[Comparative long-term spectral studies of the voice using the Lombard effect]

LTAS changes during Lombard conditions were analysed with regard to intensity level differences. Functional voice disturbances can be related to a more pronounced change of the intensity level, whereas organic voice disorders tend to display a rather limited spectral intensity change. Subjective judgement of voice quality during bilateral deafening reveals a better chance for improvement in cases with pronounced change of the spectral intensity level, i.e. primarily functional disorders. Voice changes during Lombard conditions are effected by control mechanisms compensating for the auditory feedback loss not only at the laryngeal level, but also in the supraglottic vocal tract. For clinical use the deafening procedure is of value for diagnosis as well as for therapy of voice disorders.