One of the authors discussed finite dimensional approximations to a white noise and a periodic Brownian motion with period 2 π on the projective limit space of spheres ([2]). The group of unitary operators derived from the periodic white noise has a pure point spectrum which consists of all integers with countably infinite multiplicity. We also have much interest in the investigation of a band limited white noise which is another typical example having quite different spectral type. Indeed, the corresponding group of unitary operators has a continuous spectrum with countably infinite multiplicity.