Acoustic Analysis of Bit Noise

Christian Gradl

Research output: ThesisMaster's Thesis


The goal of this thesis was to analyze the frequency spectra of noise and vibrations created at the rock/bit interface during drilling operations Previous research has shown that for certain drill bit types (PDC bit, diamond bit) the number and placement of cutting elements influences the frequency spectra of the bit vibrations. The question that this thesis aims to answer is whether these characteristic frequencies can also be found when analyzing the noise caused by the drill bit. The necessary data were collected using a test drilling rig at the Colorado School of Mines in Golden, Colorado. Before doing that, the necessary sensors had to be installed and a data acquisition system was set up. The analysis method was the Fast Fourier Transform (FFT), which is an algorithm that allows to calculate the Fourier transform of a certain data set with much less calculation time than the traditional Fourier Analysis would require. The results of the analysis showed that the measured frequency spectra of the tested drill bits were depending on the drill bit type and for drag bits also on the number and the placement of the cutting elements. Furthermore it was possible to show that there is a correlation between the rock vibrations caused by the drill bit, which were measured using a geophone, and the noise that was picked up by the measurement microphone.
Translated title of the contributionAkkustische Analyse der von Bohrmeißeln verursachten Geräusche
Original languageEnglish
  • Eustes, Alfred W., Supervisor (external), External person
Award date15 Dec 2006
Publication statusPublished - 2006

Bibliographical note

embargoed until null


  • drill bit frequency spectrum vibrations Fourier analysis noise signal processing

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