We are concerned with the inverse problem of recovering the unknown wave
speed and also the source in a multidimensional wave equation. We show
that the wave speed coefficient can be reconstructed from the
observations of the solution taken at a single point. For the source, we
may need a sequence of observation points due to the presence of
multiple spectrum and nodal lines. This new method, based on spectral
estimation techniques, leads to a simple procedure that delivers both
uniqueness and reconstruction of the coefficients at the same time.