About Alan Dauer Blumlein, the godfather of sound recording and stereo sound

The memory of humanity is selective. For centuries we will remember those who committed terrible crimes, people will not forget successful businessmen such as Jobs and Gates, show business stars will rest on their laurels of fame for decades, and after death, as in the case of King of Pop Michael Jackson, they will be mourned by the whole planet. The memory of humanity is selective. At times, we oblivion those who actually changed the course of history, but did not make a fortune on it, their contribution was not made public, they were not kindly received by world publishers and popular magazines, and the media were silent about them and are silent. The public is not interested in the identities of modest scientists, but their impact on our lives can hardly be overestimated.

Today I would like to tell you about the life and work of Alan Dauer Blumlein, an outstanding scientist of the early XX century. Alan was born in 1903 in London, in a family of German Jews who emigrated to the UK. He received a good education and became an outstanding engineer and circuit designer. Blumlane died at the age of 38 in 1942, landing in the Halifax bomber, which crashed near Herefordshire during secret tests of the airborne ground-based radar he created. An engineer could surpass Thomas Addison himself, known not only as an inventor, but also as the holder of a huge number of key patents of that time, if he lived longer and could continue his work. But to gain fame Alan was not destined, and his name may be familiar only to those involved in sound recording.

By the age of 25, Alan had become a valuable employee of the British company Standard Telephones & Cables. Blumlein’s several inventions made his employers wealthy and, if desired, the engineer could receive a lifetime salary and mess around the rest of his life. But as is the case with geniuses, the inquisitiveness of Blumlein's mind did not allow him to rest on his laurels.

In February 1929, an engineer appeared on the threshold of the Columbia Graphophone Company , now better known as Columbia Records, in search of a new job. Patent law of the time required the CGC to pay ~ 1.5 pence for each Bell Labratories record sold, a patent holder for a then popular sound recording method. In the course of his work, Alan not only invented a new recording method that saved the Columbia Graphophone Company from Bell Labs payments, but also solved the recorder's mechanical resonance problem by proposing to use electromechanical damping during recording. The technology was no longer new and was used in an acoustic telegraph, allowing you to send messages on the same line at different frequencies, but it was not previously applied to sound recording and sound reproduction. Blumlein is also credited with the idea of ​​abandoning wax master discs in favor of cellulose acetate based records.

But Alan made his most important contribution during the work on stereo sound and, in fact, its recording, being, in fact, the godfather of the modern theory of stereo sound reproduction. The problem of reproducing stereo sound originates in the principles of human hearing. No matter how many sources of sound, the human ear hears them indiscriminately. For this reason, at the beginning of the twentieth century, only one speaker was used in order not to mix sound streams and create cacophony. Alan came to the conclusion that if you exclude the time difference in the original signal, leaving only the differences in the level (intensity) of the channels, you can get high-quality stereo sound.

The inventor had two tasks: to record sound in stereo and play it in stereo. On the right you can see a note by Blumlane on a stereo recorder, in other words, a note on a microphone, also known as a Blumlane microphone. This invention made it possible to record stereo sound, instead of single-channel mono.

Blumlein's reproduction system is amazingly mono-compatible. When combining two stereo channels at the output, you get a clean monophonic mix without any unwanted color. To get clear Blumlane stereo sound, the speakers and listener should be in the corners of an equilateral triangle with sides from two to four meters. If the sound sources have a different volume, then when the sound waves are combined, a difference in levels and an imaginary delay in the audibility of the sound signal are created. At the same volume of both speakers, both incoming signals become identical, which leads to the creation of the effect that the sound comes from a source directly in front of the listener, i.e. The effect of the phantom center of sound is achieved. In order to completely shift the perception of sound in one direction,

This idea went hand in hand with another invention of Alain: to capture real spatial information when recording sound, it was decided to use combined microphone pairs. Since the carbon microphones that existed then did not meet the requirements for sound purity, to implement his idea, Blumlein, in collaboration with his colleague Holman, had to develop a new type of microphone, called the inventors “HB1A”, and subsequently coil or dynamic . The design, developed in the 30s of the last century, is still widely used in the manufacture of microphones around the world and is the most popular technology in this area.

The combined microphone “Blumlein pair” consists of two directional microphones with a radiation pattern in the form of a figure eight (see the figure below). To create a “pair” microphones must have a design in which the microphone diaphragm is open on both sides and does not respond to the absolute value of the sound pressure, but to the pressure difference between the front and rear. If you place the microphones as close as possible to each other and orient the axes of their “eights” at a right angle, you get the best configuration for stereo sound recording known today. This practice is still alive today and is widely used in recording studios.


An example of a bi-directional microphone pair (“Blumlaine Pair”) and the principle of its operation, which allows to achieve an exceptional stereo effect during sound recording.

Given the ubiquity of stereo sound in the modern world, it is surprising that the inventor of this technology is practically unknown outside the circle of people involved in sound recording.

But nevertheless, Blumein saw the film industry as the main application of stereo sound. In 1931, he and his colleagues recorded a test movie called “Walking And Talking” using stereo sound.


"Walking And Talking."

Later, already in 1935, with the participation of Blumlane, a short film “Trains at Hayes” was recorded. The short film is the first ever film with stereo sound.


"Trains at Hayes."

In the future, Blumlein’s work on stereo sound for cinema stalled: the authorities insisted on more promising, in their opinion, developments. So, the first broadcast of the BBC channel in 1936 was due to the subsequent work of Blumlane and the standard of television scan created by him in 405 lines or 50 half frames per second.


One of the first programs of the BBC, 1936.

In the name of Alan Dauer Blumlein registered 70 patents in the field of recording, processing and reproduction of sound. At the same time, this man was distinguished by amazing modesty: he preferred to remain in the shade, did not require high fees and did not detract from the achievements of his colleagues in front of his superiors. For example, the photograph used at the beginning of the article is probably the only portrait of Blumlein that has survived to this day and one of the few that existed at all. This photo was taken for his admission to the military base, where he worked during the war. Another example: when developing a new type of microphone, the first letter in the name formed from the first letters of the names of the inventors is the name of his colleague Holman, and only after that is the name of Blumlein himself (HB1A - Holman-Blumlein).

During the war, Blumlein's task was to develop a lower hemisphere radar for blind bombing using centimeter (!) Waves. Alan Blumlein died on June 7, 1942 at the age of 38 under mysterious circumstances. The Halifax bomber with a raid of just 60 hours, on the basis of which a laboratory was created to test the radar developed by Blumlein, crashed to the ground in the area of ​​Herefordshire. The causes of the crash were not established (or announced).

There is a wealth of information about the technologies created with the participation or on the basis of the work of Alan Dauer Blumlein, however, his name is almost never mentioned. There is no article on the engineer in the Russian-language section of Wikipedia, and many who work with sound do not even know how Blumlane contributed to the development of technology and the creation of the modern world.

The next time you put on your headphones and turn on your favorite song, think about who you hear this recording in stereo.

Sources:
1. Article “The man who invented stereo”, motherboard.vice.com.
2. The article "Forgotten genius", avtozvuk.ru.
3. “Hugh Robjones. Stereo Lab ”, unisonrecords.org.
4. Wikipedia.org.