According to Osho, chanting 'Om' does not bring peace—nor even the appearance of peace. What some take as calm in such chanting he calls derangement, a form of madness. He cautions that confusing excitability or trance for meditation is self-deception; true peace is not the product of mechanical repetition.
No—just repeating “Om” won’t make you peaceful; it can be a kind of craziness, not real calm.