Sound here means vibration and vibration means the nerve currents which conduct it.
There is first the external vibration, the word.
This carried inward by the sense currents, is the meaning.
After that there comes a reactionary wave in your Mind which is the beginning of Knowledge.
Memories are past impressions of Mind and may or may not create a reaction upon wave of the word hitting it.
Transcending painful memories involves transcending the reactionary wave response.
This is the practice of the Journey.