The article under discussion touches upon the issue of the English central diphthong i . This sound possesses specific acoustic features which determine its special status within the phonetic and phonological system. The scientific work presents an analysis and a description of experimental data based on oscillograms and spectrograms of monosyllabic, disyllabic and polysyllabic English words: “clear, bear, dear, ˌimmaʹterial, ˌperioʹdicity, ʹcerial”. The main goal of the present article is to highlight the importance and the common advantage of the experimental study of the central diphthong i , while studying the English language. It helps to predict many of the learners’ errors in spelling and articulation of sounds, helps to understand better the teaching and learning process. There is no corresponding diphthong in Romanian for the English central diphthong i . It should be mentioned that speakers of the Romanian language must avoid any tendencies of palatalizing, lengthening the first element or any tendencies of pronouncing the first and the second elements separately in order to have a good English pronunciation.