Densified Sounds (Technical Sheet No. 10)

Technical Sheet No. 10* — December 1983. Internal document of the Centre du Langage, presenting a key concept of the method of Dr Alfred Tomatis.*

The notion of “densified sounds” seems difficult to transmit owing to the fact that the term “densified” has not yet been sufficiently defined within our discipline. To attain a better understanding of the concept, it seems necessary to give some preliminary explanations.

Relative density and absolute density

We all know what filtered sounds are. They result from the treatment of a sonic message through filters — that is, “sound sieves”. Thanks to the filters (which suppress the low frequencies), we obtain, on the plane of the high frequencies, a density that we shall call relative density of the high frequencies with respect to the initial sound. This notion is of course opposed to that of absolute density. An example will help us better understand this process.

For a given animal population, one decides to modify the density of males and females by choosing to increase the number of the latter. However, one could carry out this operation by suppressing the male species; in this case, the relative density of our sampling would be changed, without the real density of the females in their habitat being modified for all that.

By contrast, if one orients oneself towards the solution that consists in keeping the number of males intact while increasing — by multiplication of 2, 3, 4 or n times — the number of females, the absolute density (per square metre, in sum) is thereby considerably transformed.

Another example, touching more closely on densified music, is that of considering on the one hand a musical piece played with a single violin, and on the other the same theme performed by 10 or 12 violins playing in unison. The perception is totally different. There is, in the second case, a “charm”, an opacification of the sonic object which only the term “densification” allows one to glimpse. There exists indeed an enormous difference between the sound resulting from a violin amplified by electronic means, and the sound gathered by ten violins playing in unison. The first is an increase in volume with identical internal density; the other is linked to a modification of the sonic material, in the same volume which would have greater intensity — and would therefore be amplified — but which would have changed in quality.

The densification process

The densified sounds are produced in the following manner: on an initial signal (A, Z), broad, complex, a first filtering is made which gives rise to a sound (B, Z) still broad and quite complex; from this a new matrix will be extracted which gives (C, Z), and so on up to (Z), if it please us, for example.

All the matrices are then reconnected so as to give a common recording, that is:

(A, Z) + (B, Z) + (C, Z) + (D, Z) + … + (Z)

The terminal sonic spectrum will be schematically:

A + 2B + 3C + 4D + … + 24 Z

The absolute density of each of the bands — other than (A, Z) — is thus modified. The notion of real density thus appears.

In fact, while mathematically this notion is easy to conceive, on the acoustic plane it shows itself far more complex — other phenomena being intimately linked to the very nature of the sound wave. Each of the frequencies is in fact modified, reinforced, even cancelled, by frequency couplings, interferences, phase shifts, slight displacements. So much so that, instead of reading on the spectrum a frequency F, we shall have:

F + F₁ + F₂ + F₃ + F₄ + …

… with F₁, F₂, F₃… possibly being F + 1, F − 2, F + 3, etc.

We see therefore that, by the process of densification, the pass band containing these different frequencies is thereby reinforced.

Why densify? The physiological structure of the ear

It is well to note at once that the purpose of this operation is not purely speculative. It corresponds in sum to the physiological structure of the ear. The organ of Corti, indeed, distributes its hair cells according to a logarithmic progression going towards the high frequencies. This progression is accompanied by an increase in frequency analysis, the sensitivity of which in the zone between 1,000 and 2,000 Hz lies in a ratio:

ΔF / F = 3 / 1000, with ΔI = 2 to 3 dB

It is to act on these two parameters — or more exactly on the mechanisms which correspond to them — that we have created the bands of densified sounds: densified music, densified nursery rhymes, densified Gregorian chant, densified texts, densified filtered sibilants.

Their use is to be generalised, especially when one is in the presence of listening deficiencies:

through alteration of the perception of high frequencies;
through the non-use of the charging band, in depressive phenomena;
when there is resistance to the opening of selectivity.

Currently, an apparatus developed by Pr Tomatis allows the densification of all the bands. Information on this matter will be given to us later.

Clinical indications of densified music (DM)

The bands of densified music may be used as follows:

a) Bilateral hypoacuses

after a certain number of FM sessions, in alternation with FM (balance at 10 or 7);
then continue in alternation during the SBs;
and finally, distribute at the rate of one session in 4, with filtered sibilants, FM and Gregorian.

b) Ménière’s vertigo

after the SBs, in alternation with Gregorian, FM, FM and filtered sibilants (balance to be determined — a delicate question demanding great experience).

c) Depressive syndromes

after the SBs, in alternation with Gregorian, then possibly with filtered sibilants and text.

d) Certain communication disorders

in certain autistic children, during the nursery rhyme period.

Production

Our laboratories envisage increasing the production of bands of densified sounds. However, their preparation is extremely delicate. It requires a very significant apparatus: 10 Revox 38 cm full-track tape recorders, several variable filters, etc. Each matrix demands several days of work.

Legend: FM = filtered music; DM = densified music; SB = sonic birth.

— Technical Sheet no. 10, Centre du Langage of Dr Alfred Tomatis, December 1983.