Accession Number : AD0845569

Title :   A Discrimination Study of Seismic Tunnel Echoes.

Descriptive Note : Final rept. Oct 67-Aug 68,

Corporate Author : MELPAR FALLS CHURCH VA

Personal Author(s) : Sypher, Peter

Report Date : NOV 1968

Pagination or Media Count : 94

Abstract : The purpose of this project was the investigation of several methods of signal processing intended to enhance tunnel echo indications from surface-operated seismic sounding devices. Magnetic tape recordings of pulse-echo soundings over several tunnels in the Washington, D. C. area were collected. An electrodynamic shaker was used as the acoustic source, and moving-coil geophones were used as sensors in the sounding array. Signal processing techniques included spectral analysis, cepstrum and correlation analysis, and frequency filtering. The results of the analysis of data collected over three tunnels were not as definitive as originally expected. Crosscorrelation of sensor outputs appeared to enhance echo indication in the case of one tunnel. (Author)

Descriptors :   (*ACOUSTIC SIGNALS, UNDERGROUND STRUCTURES), ACOUSTIC DETECTORS, NOISE GENERATORS, SOUND TRANSMISSION, UNDERGROUND, CORRELATION TECHNIQUES, MAGNETIC TAPE, RECORDING SYSTEMS, EPICENTERS, RANGE(DISTANCE), TIME, VERY LOW FREQUENCY, EXTREMELY LOW FREQUENCY, DETECTION, ECHO RANGING.

Subject Categories : Acoustic Detection and Detectors
      Seismic Detection and Detectors
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE