AUM is called the soundless sound because we do not strike any object with any other object in order to produce it. Because it is unstruck, it is known as the soundless sound. In Sanskrit, this phenomenon is called Anahata, which means literally 'unstruck'. We can hear the sound in the inmost recesses of our heart, but we ourselves do not do anything to create it; it is created spontaneously. We only receive AUM or hear it.
On the physical plane AUM is a physical sound like any other sound. But permeating the physical sound is a higher divine vibration. This spiritual vibration comes from its connection with the inner reality of the universal AUM, which is the life-breath of the whole creation.
We call AUM the soundless sound although with our ordinary ears we may hear this sound produced in the ordinary way in the outer world. But we can also hear it in the inner world if we have a special kind of hearing. We can hear the unstruck AUM with our spiritual ears. It is not the same sound that we hear with our physical ears. The inner AUM comes from an inner world and its sound is altogether different. With our human ears we cannot hear it. We must have a different type of hearing if we want to hear the true soundless sound.From:Sri Chinmoy,A life of blossoming love, Agni Press, 1992
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