  It is shown how wavelets may be used to analyse the absorption properties of
the Lya forest. The Discrete Wavelet Transform of a QSO spectrum is used to
decompose the light fluctuations that comprise the forest into orthogonal
wavelets. It is demonstrated that most of the signal is carried by the moderate
to lower frequency wavelets in high resolution spectra, and that a
statistically acceptable description of even high signal-to-noise spectra is
provided by only a fraction (10-30%) of the wavelets. The distributions of the
wavelet coefficients provide a statistical basis for discriminating between
different models of the Lya forest. The method is illustrated using the
measured spectrum of Q1937-1009. The procedure described is readily automated
and may be used to process both measured spectra and the large number of
spectra generated by numerical simulations, permitting a fair comparison
between the two.
