Tech UPTechnologyIn search of memory: light and sound

In search of memory: light and sound

It is curious that the octogenarian Cajal, who so bitterly —and rightly— criticized the rote teaching methods of his childhood, persistently pursued memory in his maturity. On the one hand, indirectly with his research on neurons; on the other, with the need to capture in a drawing what he saw or imagined and, finally, with his passion for photography and a slight adventure with acoustics.

Given his penchant for novelty, it is not surprising that Cajal could not resist the craze for the new invention, the phonograph . He got hold of one and in his spare time he set out to make sound recordings, recording family, friends and children to whom he gave coins for that purpose. He even recorded famous people, “forcing them to impress ballads, songs, and comic lines.” Pepe Zahonero (doctor, lawyer, writer and journalist) and Francisco Romero Robledo (important politician of the time) passed through his phonograph.

Unfortunately, we do not keep any of the recordings . However, those early recordings of the nascent technology were crude and of low quality. A result that Cajal was not entirely happy with, since the sound even seemed comical or unpleasant. To see something new you have to change your perspective. Galileo directed a telescope to the Moon and Cajal was not going to be less: he focused a microscope towards the very heart of the sound record of the phonograph. To see what he observed, let us first recall some of the history of the phonograph.

The revolutionary phonograph

Without a doubt, in its day it was a revolutionary invention that influenced culture, science, art, industry and commerce. Today we are used to sending comfortable and high-quality audio messages, but at the end of the 19th century the simple idea was science fiction. The first to record the voice in some kind of support would go down in history.

Although there were European antecedents —such as Leon Scott’s phonautograph—, it was Edison who was the first to patent and market the phonograph, in 1877 . Etymologically, phonograph means something like “writing the voice” and it is literally what the device did. Sound waves are transformed into mechanical vibrations by a transducer. The mechanical vibrations thus obtained cause a stylus to oscillate, which carves out a helical groove in a cylinder that rotates with the help of a crank. This same system in reverse was used to reproduce the recorded sound. Regarding the cylinders, the first ones were made of cardboard and were covered with tin, then waxed cardboard was used and finally solid wax was used, which was of higher quality and durability.

The phonograph has a built-in speaker as an amplifier that has a diaphragm and a needle. To record, the vibration of the sound wave is transmitted to the diaphragm, this activates the needle, which spirally shapes the vibrations on the disc. For reproduction, the mechanism is reversed: the needle is placed at the beginning of the groove, the cylinder is activated by the crank, the recorded vibrations move the diaphragm and it amplifies the sound waves through the horn.

Despite the lack of initial quality, the phonograph became the first acoustic memory in history and forever changed our ways of life. Edison himself went so far as to say: “It teaches us to be careful and follow through on what we say, and I’m sure it makes men more concise, more professional, and more direct.” 19th century Twitter, come on. The phonograph came to open the era of auditory, objective and collective memory.

Tewksbury’s famous manual consisted of 90 index entries, that’s how complex the device was. Among these parts were a camel hair brush and a bottle of lubricating oil. And it was very important that there were no dust particles in any of the elements, in addition to regular cleaning and greasing of the dynamic parts. The objective was none other than obtaining a record of the highest quality within the possibilities. And this is where the restless mind of our Nobel Prize winner comes in. Don Santiago could not contain his creative impulses and wanted to find a solution to the aforementioned low quality of the phonograph.

Cajal and how to improve sound quality

What he did in the first place was to put the cylinder impregnated in wax under the microscope , to make a millimeter study of the grooves left by the needle. He worked on what might be called a high-sensitivity or high-fidelity phonograph record. He came to devise a recording system in which the cylinder was replaced by a flat disc, possibly prior to Berliner’s gramophone patent. He carried out his experiments with the phonograph between 1895 and 1896, in a playful environment. Which, in his own words, “provided him with delightful winter evenings.”

Cajal quickly realized that the voice was reproduced with an almost natural timbre and modulation , but with a great deal of volume. If one wanted to intensify the impression and spoke or sang close to the horn, the voice was “screeching, shrill, and unbearable to any sensitive ear.” It seems that under the microscope he had found the cause of the stridor, as he recounts in his Memories : « As revealed by the most superficial microscopic examination of the grooves, it depends on the engraving stylet, instead of carving a continuous, undulating canal in the wax in the sense of depth, he sculpts isolated and deep pits, separated by spaces clean of all impression. From which it can be inferred that the diaphragm, during its energetic swinging, records only half, and sometimes less, of the sound undulation, without the secondary curves of the harmonic notes that are essential for the good translation of the timbre. And such a defect is irremediable because of the hardness of the inscription material. The use of a wide cylinder somewhat attenuates, but does not correct, the aforementioned defect”, he explained.

In search of high fidelity

Ramón y Cajal’s concern for high fidelity is pioneering, taking into account that the term would be created in the 1920s by some manufacturers of radio receivers and phonographs to distinguish normal devices from those that reproduced perfect sounds. In the Museum of the Cajal Institute (Madrid) some handwritten pages are kept with annotations of a draft of an article by him in which he dealt with these aspects of acoustic fidelity as well as advice for an adequate recording with the phonograph .

Santiago Ramón y Cajal was not satisfied with finding the basis of the error of quality, but rather — typical of a creative mind — he sought a solution. He comes up with the idea of exchanging deep writing for flat writing. The tracing on a metal or glass plate of a continuous or sinuous line would be the big difference with the previous model. He calls it a “disc phonograph” , but it is actually almost a full-fledged gramophone (using discs instead of cylinders), before this device was available on the market. But unfortunately his ingenuity did not find the necessary help in Spain, “due to the almost impossibility of finding workshops where delicate and highly precise instruments are built.”

He did what he could and describes it this way: «Enthusiastic with the idea, I commissioned an unskilled machinist (in the absence of a precision mechanic) to build my disc phonograph, while I tried practical methods of molding in gelatin, wax or celluloid. Unfortunately, the device, if it fully confirmed the new registration principle and the presupposed advantages, worked deplorably. And requested by more pressing occupations, I forgot the unfortunate device, which I threw away in the attic waiting for a mechanic capable of understanding me. As well; the device imagined by me, and partly built during the years 1895 and 1896, I found brand new and recently released to the public under the name of gramophone in a certain store in New York. Later disclosed throughout the world and exploited by the American Gramophone Society and its European daughters, this device served as the basis for a splendid business, encrypted in many millions. I do not refer to these things out of puerile vanity, but so that my biologist, medical or naturalist readers learn at my expense not to waste time pursuing inventions outside the circle of their own competence».

The microphone: light and sound united

Cajal’s experiments on the reproduction and amplification of sound have not all been lost. In 1903 he published the article The phonograph and the microphonograph , in the magazine La Naturaleza . The adventure of his new invention ends here, due to a coincidental and fatal historical event. Cajal noted in his article: «Scientific works of another genre and, more than anything, the news, read in the yearbook of photographic novelties, that M. Edison, the famous inventor, had obtained an invention patent by a procedure analogous to ours, they made us abandon the work, despite the encouraging results achieved».

The new invention to which Cajal alludes could be called a photophonograph, that is, it would be made with a technique that would combine optics with acoustics: “The essence of the problem does not consist in obtaining a photograph of the sound vibration, since such an undertaking constitutes a plain experience. and current in physiology laboratories, but in transforming the black stripe of the sensitive plate into a groove capable of guiding the index of the reproductive membrane. Poitevin’s bichromated gelatin was used for this purpose, and I thought I was the first to do it, with which photo-reliefs can be easily obtained (from Woodbury). But when I had just heard my frames (about four or five years ago), I knew that the illustrious American physicist had used exactly the same resource as me. Then I got rid of a job that had lost the incentive of originality».

Cajal’s unsuccessful photophonograph was an improved gramophone , in which the problems of lack of sensitivity were attenuated and which was “capable of recording speech delivered at a moderate distance, and even conversations in a natural voice”. He used a thin sheet of mica as a membrane.

To solve the problem of voice amplification, the Spanish invented the microphone , which is the first scientifically based amplification device in history. In this case, the sound is transferred through the needle to a rotating disk of glass blackened by the flame of camphor. A very fine needle scratches the carbon black and the obtained engraving is varnished. A copy is made by the collodion method, two or three times larger, after which a photorelief of the enlarged copy is obtained (glass covered with bichromated gelatin). The collodion method is a photographic procedure widely used in its day for developing photography. The memory of light and sound united by a wonderful mind, that of Santiago Ramón y Cajal.

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