Modified Amplitude of Gravitational Waves Spectrum
  The spectrum of thermal gravitational waves is obtained by including the high
frequency thermal gravitons created from extra-dimensional effect and is a new
feature of the spectrum. The amplitude and spectral energy density of
gravitational waves in thermal vacuum state are found enhanced. The amplitude
of the waves get modified in the frequency range (10$^{-16}$ -10 $^{8}$ Hz) but
the corresponding spectral energy density is less than the upper bound of
various estimated results.
  With the addition of higher frequency thermal waves, the obtained spectral
energy density of the wave in thermal vacuum state does not exceed the upper
bound put by nucleosynthesis rate. The existence of cosmologically originated
thermal gravitational waves due to extra dimension is not ruled out.
