The Rasa’il Ikhwan al-Safa - The Epistle on Music
Type of Spiritual Experience
The Brethren of Purity were a community in Basra, Iraq whose greatest contribution to learning at the time they were working in the tenth century, was an encyclopaedia of knowledge. At the time they wrote their treatises, the musical instrument the 'oud' was in use and as we see in the quote had been tuned to the perceived sound of each 'level'.
What we can see in this quote is that the levels 'closest 'as it were to the Earth itself can be heard as notes which are capable of being expressed using a musical instrument. In our modern terminology they can be heard as 'sound'. What then appears to happen is that as a person goes figuratively 'higher' up the storage levels, the sound becomes inaudible as it starts to enter the realms of ultrasound. What I have also found is that as a person 'descends' figuratively in the storage system, the noise also becomes inaudible, but then becomes infrasound – low frequency sound that is also inaudible to us.
A description of the experience
The Epistle of Music of the Ikhwan al-Safa' translated by Amnon Shiloah source Joscelyn Godwin
We return to the subject we are treating and we say; the musician philosophers limited themselves to four strings for the oud, no more, no less, so that their productions would be comparable to the natural things that are under the lunary sphere and in the image of the science of the Creator... In effect, the first string is comparable to the element of fire, and its sonority corresponds to the heat and its intensity. The second string is comparable to the element of air and its sonority corresponds to the softness of air and its gentleness. The third string is comparable to the element of water and its freshness. The fourth string is comparable to the element of earth and its sonority corresponds to the heaviness of earth and its density....
...........physicists advance the theory that the diameter of each of the spheres of the four elements...... is in the proportion of 4:3 with the diameter of the sphere below it... this means that the substance of fire is in the proportion of 4:3 with that of air; that the substance of air .. is in proportion of 4:3 with that of water and that the substance water, is in the proportion of 4:3 with that of earth.