In this paper we present vibratory characteristics of a typical concrete pedestal cast over bedrock in a ground floor room of a large laboratory building at our Centre, to mount a sensitive spectrometer on it. Around this pedestal is provided a rectangular channel of small width filled with dry sand as vibration damper. In a seismic experiment, the vibration Isolation response (transmıssıbılity) of this pedestal has been measured and interpreted. The transmissibility has been computed from power spectra of artificially generated transient signals produced at the time of the experıment by dropping a small weight on the floor and detected simultaneously by seismic sensors installed at the base as well as at the top of the pedestal. Essentially, the coherence between such pairs of signals has been used to interpret the transmissibility peaks. From the wide band accelerographic data, the pedestal is found to have appreciable transmissibility in the frequency band 90-110 Hz peaking at 102 Hz.