The sound of OM is referred to as the Pranava.
Here are two interpretations of the word Pranava: One, Pra ("before") nava ( "sound of joy") and two we see the Prana in Pranava and interpret Pranava as the life giving sound.
Om is a composite of the letters A (as in father) U (as in flute) and the M vibrates like the mmmm sound we make when we bite into a ripe fruit.
It can be chanted as OM or AUM and in fact has many official variations.
When chanting the sound of OM we begin with our consciousness at the heart, in the middle, consciousness is at the back of the throat, with the M sound we are focused at the point in between the eyebrows and at the end, the silence, we are focused at the crown of the head.
When we say: "ahhhh" the mouth is open representing beginnings and creation.
When we say: "ouhhh" the mouth closes a little and the sound is felt at the back of throat representing preservation and the middle process of life.
When we say: "mmmm" the mouth closes representing endings and dissolution.
The pause at the end is a reminder of the natural beginnings, middles and endings of life and of the aspect of life that is untouched by the process of nature.
In addition, in everyday life when we spontaneously say: ahhhh, ouhhh and mmmm, it's because we are happy and welcoming the beauty of life. With these sounds we are in essence saying YES to life and AUM connects us with that energy.
So much has been written about the meaning of OM. It's good to read, chant, listen - pause and start again.
The word Pranava also represents our unique YES sound. It is the sound me make when we are in presence, connected and receptive. If we learn to listen for it, feel it and express it freely we tune in to our unique vibration, reduce judgment and create a ripple effect, inspiring authenticity.