INDIA, May 8, 2017 (Times of India): Do you love the art of chanting sounds? Are you one of those whose day starts with reverberating sounds of Om? Then this may appall you because it is not Om that you must chant; it is Aum. Meditation experts say that the Sanskrit word Aum has, over a period of time and owing to the ravages of spread and travelling, has become Om. And this isn’t make-believe; there’s science behind it.
Om is basically a monosyllabic word, as compared to Aum, which is tri-syllabic. This is because of the difference in the way the two words are pronounced. Om is simply pronounced the way it is written. Against this, Aum is pronounced as aa-uu-eemm. The idea behind chanting certain sounds is that they cause vibrations in our body. This has a corollary in science where scientists see the entire universe as reverberations of energy. This translates into the entire existence as being an amalgamation of sounds.
Source: http://www.hinduismtoday.com/blogs-news/hindu-press-international/you-have-been-chanting-it-wrong–it-s-aum–not-om/15793.html