We consider half-line media which consist of many kinds of
substances. We assume that the waves through this media are
described by the one-dimensional wave equation. We can directly
observe the data near the boundary point of the half-line,
but we cannot directly observe the data of things away from
the boundary point. In this situation, we try to identify
these unknown things by creating an artificial explosion
and observing on the boundary point the waves generated by
the explosion. In the previous works related to this problem,
only the speeds of the waves were treated, but we also take
into account the impedances of the media in our setting.