A task force of contractors, NASA agency representatives, and MSFC researchers concluded that the engines vibrated at a frequency similar to the frequency at which the spacecraft itself vibrated, causing a resonance effect that induced oscillations in the rocket.
ɐ tˈæsk fˈoːɹs ʌv kəntɹˈæktɚz, nˈæsɐ ˈeɪdʒənsi ɹˌɛpɹᵻzˈɛntətˌɪvz, ænd ˌɛmˌɛsˌɛfsˈiː ɹᵻsˈɜːtʃɚz kəŋklˈuːdᵻd ðætðɪ ˈɛndʒɪnz vˈaɪbɹeɪɾᵻd æɾə fɹˈiːkwənsi sˈɪmɪlɚ tə ðə fɹˈiːkwənsi æt wˌɪtʃ ðə spˈeɪskɹæft ɪtsˈɛlf vˈaɪbɹeɪɾᵻd, kˈɔːzɪŋ ɐ ɹˈɛzənəns ɪfˈɛkt ðæt ɪndˈuːst ˌɑːsɪlˈeɪʃənz ɪnðə ɹˈɑːkɪt.