  Recent advancements in synthetic speech generation have led to the creation
of forged audio data that are almost indistinguishable from real speech. This
phenomenon poses a new challenge for the multimedia forensics community, as the
misuse of synthetic media can potentially cause adverse consequences. Several
methods have been proposed in the literature to mitigate potential risks and
detect synthetic speech, mainly focusing on the analysis of the speech itself.
However, recent studies have revealed that the most crucial frequency bands for
detection lie in the highest ranges (above 6000 Hz), which do not include any
speech content. In this work, we extensively explore this aspect and
investigate whether synthetic speech detection can be performed by focusing
only on the background component of the signal while disregarding its verbal
content. Our findings indicate that the speech component is not the predominant
factor in performing synthetic speech detection. These insights provide
valuable guidance for the development of new synthetic speech detectors and
their interpretability, together with some considerations on the existing work
in the audio forensics field.
