Various problems of electronics
Various problems of electronics — Paper and discussion (Mr Karsenty, Société Hi-Fi) — 2nd International Congress of Audio-Psycho-Phonology, Paris (1972)
Sixth communication of the 2nd International Congress of Audio-Psycho-Phonology held in Paris from 11 to 14 May 1972. Mr Karsenty, engineer of the Société Hi-Fi which has taken charge of the manufacture and after-sales service of the devices linked to the Electronic Ear, presents in a few minutes the choice of the REVOX tape recorder in a special version (single-track, 9.5 cm/s) and then engages in a technical discussion with the Centre directors (Mr Mapples and Mr Lippelen from Ottawa, Mr Dubard from Nice, Mme Joanny from Nancy, Mr Madaule of the Paris Language Centre) and with Prof. Alfred Tomatis himself. The questions raised — cross-talk on double-track tapes, calibration of the playback heads, the myth of stereophony, passive filters cutting at 2000 Hz, active filters attenuating 50 dB then under development, standard wiring diagram (Electronic Ear, tape recorder, filters, Audio-Stimulator), risks of haphazard modifications — give a rare glimpse of the technical culture of an APP Centre network at the turn of the 1970s and of the rigour Tomatis required of it.
“Various problems of electronics” — Paper and discussion
Mr Karsenty (Société Hi-Fi)
Sixth communication of the 2nd International Congress of Audio-Psycho-Phonology, Paris, 11-14 May 1972 (Friday 11 May afternoon).
Mr Karsenty’s opening paper
Mr KARSENTY. — I should like to begin by saying that, after many trials concerning recordings, we have concluded that there were several very important points not to be neglected in the perspective of work carried out with the help of the Electronic Ear.
Numerous tests have been carried out on a great number of tape recorders commonly available on the market, and these studies have led us to adopt a device which, even if it is not appreciated by all, fits perfectly with the requirements of the Electronic Ear.
We have thus been able, with the help of our Swiss and German friends, to develop this REVOX tape recorder in a special version. The latter will allow the use of a device at the speed of 9.5 cm/s with single-track tapes. Why adopt this solution? First because it will give us the possibility of using the tapes in their entirety; there will be no blanks; we shall thus make savings by working at 9.5. Furthermore, there will be less risk of deterioration of these tapes, and the problems of cross-talk will be avoided, problems that always exist when one wishes to use 2 or 4 tracks. We shall also avoid certain drawbacks such as wow and flutter.
After these few words, I leave the floor to those who would kindly put technical questions to me.
Discussion
Mr MAPPLES (Ottawa). — (Question not recorded.)
Mr KARSENTY. — No, that has not been envisaged for the good reason that the passband required for this tape recorder, at least as regards the work in question today, does not oblige us to work beyond 14 or 15,000 Hz; this whisper that people might have reproached the recordings we have made so far probably came from the magnetic tapes you have used. If it is sparingly that people commonly used unmodified tapes that one must use, on the other hand, we ask the users to operate the device at 9.5 with single-track tapes. Very often recordings made from 2- or 4-track tapes, for reasons of economy not satisfied by that, is what I deplore the value given the requirements imposed by the Electronic Ear.
Prof. TOMATIS. — I think the present interest would be to use full-track tapes, so that we may have a much wider band and obtain a better dynamic, even by going at a lower speed.
This solution may bring about a considerable saving in tape, which is not to be neglected from various points of view. First, the cost related to the space necessary to store the tapes. Given the evolution of the programmings, a very large number of tapes is now indispensable for each Centre, and it is well to think here of a storage problem.
Moreover, if one uses double-track tapes, one must not forget that there is always the risk of the unused track. Otherwise, if one were to record something on the second track, one runs the risk of causing cross-talk — that is, in the same way the first — and provoking erasure phenomena, and so on.
We have tested a great number of tape recorders; the REVOX is the only one to meet near-professional standards, in accordance with the use we make of it within our technical Centres, and we wish for devices that are worth a fortune for a quality that is not always the most sensible.
Mr LIPPELEN (Centre for the Study of the Child, Ottawa). — (Question, followed by the reply.) — At one time, the tape recorders in permanent and uninterrupted use with us presented problems of head adjustment that were difficult to master. For us this is also a concern, but if the future, as Mr Karsenty and Prof. Tomatis have said, the after-sales service of the Germans, who are willing to ensure the maintenance of these machines, should at last come to our support on this matter. If one day a REVOX tape recorder were to break down, Mr Karsenty’s team will ensure its immediate replacement, so that it will always be possible to keep permanently in each Centre a complete set in working order.
Prof. TOMATIS. — You know that, for all of us, users of the Electronic Ear, the problem of tape recorders is very important, since sound information is most often distributed from tapes recorded on a tape recorder. If the device breaks down, we find ourselves strongly immobilised. There remains only to have the subject read under Electronic Ear, which I did indeed for a long time at the beginning of the setting up of the techniques.
Mr Karsenty is therefore now setting up a system of after-sales service, of putting into operation and of supervision, which will help us considerably on the technical plane.
Mr DUBARD (Nice). — Are the REVOX you use those of the 77 version, or something else?
Mr KARSENTY. — Yes, but they will be modified, since we shall convert them to single-track.
Prof. TOMATIS. — I think that is easy. The German engineers showed us how to proceed to convert to full-track; the recording head must be changed, but the devices used are the same as those you have.
It must not be forgotten that a tape running at a lower speed wears out much less quickly; this too plays a part and provides a further advantage. The danger would of course be that, if one were to change the speed on existing tape recorders, there might be a perceptible drop in the desired effects. But the REVOX technical team has carried out very thorough measurements on this point and has undertaken to comply with the standards necessary for the proper functioning of the Electronic Ear.
I think it is well to specify that by reducing the speed but broadening the entire band to single-track, we obtain results superior to those of a double track. Do not forget either that a full track is more than twice a half track, contrary to what people think, since there are the two tracks added, plus the empty middle; the full track gives a percentage of 1.2 more, which considerably increases the dynamic.
I should like finally to specify that, if one wishes to use the full track and moreover to keep the 19 cm/s speed, the quality can only be further improved, since we thus approach absolute criteria.
Mme JOANNY (Nancy). — From what you tell us, the double-track tapes must not be recorded on both tracks?
Prof. TOMATIS. — No, it is better not to, for you risk introducing errors by passing other information at the same time and by triggering cross-talk phenomena — that is, one piece of information may interfere with the other. Suppose that one day you have a full-track tape recorder and that you play the tape recorded on it on another tape recorder whose heads are not exactly calibrated; you then risk playing something other than what is necessary.
From time to time we are sent from the provinces or from abroad recordings to be filtered which we are obliged to return without having used them, because they contain little noises of birds or ducks of which it is impossible to be rid. People find these technical problems difficult to understand and do not realise how necessary it is to be very demanding in the matter. I remind you once again that we work, we treat, we help by means of sounds, and that, by reason of that, we must be very attentive to the value of the transmission of this sonic material. I lastly specify that 4-track tape recorders are not usable in our techniques.
Mr KARSENTY. — For the Centres that wish it, it will be possible for us, in some time, to modify the REVOX 77s that are now double-track, and which we shall probably be able to convert to full-track.
In reality, a tape is 6 millimetres high; when you make a recording on two tracks, these are about 2 mm each. Now, when you make a full-track recording, you will have a surface that will be a good 5 mm or 5.5 mm.
Prof. TOMATIS. — I should like briefly to raise the problem of stereophony, which is, as you know, a very fashionable problem. We are well placed to know that stereophony does not exist in the form attributed to it today. It is another phenomenon; it is a temporal shift in the entry of the subject into listening; it is not a phenomenon imposed externally, and as a result it is useless for us to make use of several tracks. That makes us use capital for nothing. We always go through the same channel, the Electronic Ear, and it is the latter that will do the dispatching to bring forth the true sound relief that must engage the consciousness of the body schema necessary for the entry into listening.
A Listener. — (Question on filters and the filtering of maternal voices.)
Prof. TOMATIS. — Another important question must also be raised on the technical plane: the one raised earlier by Mr Mapples concerning the tape transport and the background noise the latter may produce. In carrying out filterings, we noticed that this background noise was very often linked to the quality of the tape. You know that a magnetic tape is made of plastic coated with iron filings; when the information passes over these iron filings, it then takes one or another direction of polarity. If you go too fast and there is not enough information, you realise that the plastic that seems homogeneous to the naked eye is in reality not homogeneous when one looks at it under a microscope or an enlarger; there are hollows and voids.
You see therefore that, on the whole, the problem of tapes seems practically resolved. Furthermore, Mr Karsenty has kindly agreed to take charge of the supply of tapes for all the Centres, so that you can apply to him directly to obtain quality material on very favourable terms. It is a great problem when one uses a great number of tapes, who prepares numerous sonic births (?), 5 and even 6 tapes are sometimes needed for each child and who apply very varied programmings. By using, with this new formula, half as many tapes, one can thus make a considerable saving on the costs of tape and on the space required for storing tapes.
A Listener. — I should like to ask you how this is done in the Centres for the filtering of maternal voices.
Prof. TOMATIS. — By using non-variable filters cutting below 2,000 Hz. We are now developing active filters going up to 50 decibels of slope; one reaches 50 decibels, it is not a true cut but a cut at a certain low frequency, and it happens that the information passes nonetheless. We realised that, when one believed one could not get it down to 50 dB, there was always something passing. The filter we use now is at 40 dB; there is no doubt that, from time to time, if the voice of the mother who speaks an infant’s voice, too many low frequencies pass, there is not enough information; and the filtering is not sufficient. One is obliged to over-filter, which complicates life; then there is nothing left of the information, save the possibility of extending it on one side and pre-cutting on the other, as we are now having done — a variable filter for the needs; and why, in a few months, we shall be able to offer you a quality filter. It will be a universal filter cutting up to 50 decibels.
I think nonetheless that it should be specified that what we practise is not exactly a filtering — that is, a cut above certain frequencies — but rather a modification of the information, the sum of energy remaining the same. That is what appears, what seems very simple at first sight but which the electronics engineers cannot conceive. I know it is a delicate problem, on which I have been working for many years.
The notion of filtering must therefore be taken up in the sense of a modification of the information, not a cut. We know that, sometimes when one cuts, one strikes a reef — that is, nothing remains of the picture given; and one fits too small a filter, one cuts the information; that is not our aim. It may be that the child hears less during his foetal life than after his birth; he hears as much, but in another way. That is what we wish to obtain — that is to say, a modification of the incoming information, by translation again at another level.
This corresponds, on the physiological plane, to a determined tension of the eardrum that brings about a posture posited of impedance adaptation, as do certain devices called “impedance-matching” devices which, in fact, are well designed — that is, do not cause a diminution of energy. That is where the difficulty lies, for, despite all the progress of electronics, there is still nothing resembling a human ear. The latter is a work of impedance adaptation, and in a quasi-instantaneous way, this work of impedance adaptation. You see that we are still far made as by an electronic machine!
We have also asked Mr Karsenty to develop a kind of standard set-up with all the connections: Electronic Ear, tape recorder and filters, so that no error of assembly may henceforth creep in. The task will in this way be simplified for those who are not very versed in electronics. There will thus be no risk of mistaking buttons, wires, connections, impedances, and so on.
As we work with high-precision instruments and equipment, we must see to it that the set-ups are perfect. The introduction of the slightest error may compromise a treatment — that is, sometimes the future of a subject. It is therefore very serious, and that is why we must be very demanding. We are counting on Mr Karsenty to offer us sets of good quality, including on the technical plane. We have at our disposal a device of great quality, the Electronic Ear, and we must see to it that the rest of the set-up is equally perfect. I have noted on several occasions, in going to consult at certain Centres, that the set-ups had been tinkered with by the local electronics technicians, who had seen fit to make innovations to advertise themselves, totally ignorant of the very particular aim it was desired to reach. I have seen, among others, in one Centre, REVOXes that had been tampered with and supposedly improved. The drawback is that there was nothing left at the output.
I have also seen people try to modify the Electronic Ear and improve it. That has never given anything but catastrophes. It must not be forgotten that the Electronic Ear was elaborated in accordance with physiological reasonings that one is not yet in a position to modify. We shall perhaps have to wait for a new era to attempt to make another device. Content yourselves with what has been developed and has proved itself on thousands of cases. The improvement to be made must now focus on the quality of the tape recorders, of the filters, of the set-ups, of the recordings and also of course of the tapes. In certain Centres, recordings of poor quality, filtered affinities for instance which had lost their characteristics, their effects, and all this on the pretext that one had wished to save money by buying tapes on the cheap. Such errors must absolutely be avoided. Each Centre director must observe strict rules as to the quality of the material he uses for the Electronic Ear. Otherwise, it is better that he give up helping people in this way and that he take up another trade. One has no right to tinker when the future of a human being is at stake.
We are therefore counting on Mr Karsenty — who already provides us with tape recorders of quality — to offer us well-studied set-ups and models that each user can procure if he wishes.
Mr KARSENTY. — Indeed, at the request of the people who are on the continent, I could possibly travel and see on the spot what their own problems are.
Prof. TOMATIS. — That is an excellent solution which will certainly be of service to those who have set-up difficulties.
As regards the Centres on the other continents, Canada for instance, we shall pass on all the information to them so that they can in their turn have the set-ups and sets studied on the spot. For Mr Mapples for instance, we shall transmit information to him so that he can develop the set-ups, standardise them and distribute them in Canada and North America.
Mr MADAULE (Paris Language Centre). — The new single-track tapes you speak of, are they ordinary tapes?
Mr KARSENTY. — Yes, they are ordinary tapes available on the market. They have their own references.
Mr MADAULE. — Will they last half an hour, like those we now use? If they are recorded full-track, they seem able to last an hour.
Mr KARSENTY. — It is certain that the same length of tape can serve you twice — or, more precisely, that you can make two half-hour tapes from a single single-track tape.
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Source: 2nd International Congress of Audio-Psycho-Phonology, Paris, 11-14 May 1972 — Communication No. 6 by Mr Karsenty (Société Hi-Fi), “Différents problèmes de l’électronique” (paper and discussion), pp. 96-103. Document digitised from the personal archives of Alfred Tomatis. A few passages present defects of OCR or of the original typewritten transcription; they have been kept as close as possible to the source text, with an effort towards readability.