Question about how analog audio recording works
Hello!
My wife and I are high and having a discussion about how sound is recorded on records. I have an, I think, more than average understand of how sound and recording/playback works so I was trying to explain how grooves on the record represent sound waves.
What we don't understand is how polyphony is physically represented. So I can see how a single sine can easily be represented on a record. But when you're talking several sounds at once, some on the same pitch some now, dozens of timbres happening all at once, how do we differentiate those sounds on a physical medium like vinyl, or how do we represent it digitally? Is it literally nothing more than 1s and 0s? That'd be sick
Anyway, I hope this makes sense. Thanks!
Science rules !! Just conceptualize the various process involved from capturing the music to making the disc (cd and vinyl) to playback thru a system. Here is the very first recording ever made from France"Au clair de la lune" 1861.www.firstsounds.org/sounds/Scott-Feaster-No-36.mp3 The march of science. |
I’ll bite. In any analog medium, waves are superimposed on each other. For example, in water you could have small high frequency waves and large low frequency waves and what you would see would be big waves with multiple little waves on top of them. For sound waves it is basically the same. Imagine a line with a bunch of small wiggles in it. Now imagine the whole line being bent (with those small wiggles still intact) into a much more gradual, large wave. Now you have the visual equivalent of two tones — a low tone represented by the broader up and down and a high tone represented by the smaller wiggles superimposed on the broad up and down. If you looked closely at the groove of a record you would see this same thing. A mono record is easier to see it since it is a one dimensional wiggle. You would see a broad gradual wave in the groove, with a smaller, more closely spaced wiggle in it. The cartridge translates this to an electrical signal, which gets boosted in stages before it gets translated into driver motion, passes through the air as compression waves, and then translated back into motion at our ear drum. We then perceive this as two separate tones because we have hairs in our ears that are tuned to different frequencies, and those nerves send differentiated signals to our brain, which does some amazing magic to process those signals into the perception of hearing a two tone sound. |
For all purpose in life and for the average "us" the above post is enough... But to goes further the links i put are very illuminating about the complexities of this problem...
By the way in an audio system well put and under control, we "see" the sound in the room, our brain translate chords into imaginary perceived but very real dynamical VOLUME... It is like a rainbow perception a "real" illusion not a misperception, or an error or a meaningless accident but a phenomena at the frontier where the mind encounter the world and translate it from inside ... My K340 headphone did this as well as my speakers in their acoustically controlled room did it , then sound is not only an abstraction created by the brain and the wacves, not only a felt vibrating string on a plane , nor a mere vibrating and oscillating surface, but a volume too and more...Acoustic and psycho-acoustic are so deep that even today there exist many unanswered problems about hearing ... For example this articleabout decoding perception by the brain: https://phys.org/news/2013-02-human-fourier-uncertainty-principle.html Readers of the Bible know that the first sound play the first role in the creation in "Genesis and in ST-John where Logos is not an abstraction only but a "sound" and a "voice" ...As in Indian vedas the sound "OM" contains the universe... This is not only mere superstition but deep spiritual intuition about sound...And Sound contain information and memory as Babies listening the world decipher it way before seeing it... Etc.. Sound qualities are heard and convey many information about the fruit if we tap it to know if the fruit is ripe or not...We can deduce hearing his sound if the tapped object is made of steel or wood and if he contains aperture, one or many, and if the object is empty completely or dense etc... Sounds is information not a mere wave abstraction...Sound is quality not only quantity... But anyway numbers are qualities too as in Pythagoreanism and Platonism for example through their connection to shape and then qualitative symbolism by a primal Cenesthesia...
To answer this question mathemathically is very hard....Most of the question and some answers can be found in Marc Kac article," Hearing the shape of a drum" and there is an interesting and very deep confrence by Alain Connes, a true genius, founder of non commutative geometry...Keep his French name in your mind if you are a young student in physics or maths... here the wiki stating the maths problem in two paragraphs: "the shape of a drum" https://en.wikipedia.org/wiki/Hearing_the_shape_of_a_drum
Marc Kac article put the problem in front of your eyes: https://www.math.ucdavis.edu/~hunter/m207b/kac.pdf Now deeper and life changing but very hard to figure out if you are not a physicist or a mathematician, Alain Connes go under the belly of this question and think about TIME and Information among other matter in this conference title "Seiing shapes" ... It is translated in English from the french original...Very deep...I must listen to it anew because it is very hard and i forgot it after few years...( i am a philosopher not a mathematician but maths is one of the key to philosophy for me) |
Yours is a question that you can see the answer or you can’t. Some people’s brains are geared differently and they can see things. Take Albert Einstein, he figured out the theory of relativity in his head! And with all the computers we have now, we still can disprove it. How did they figure out the speed of light so he could figure out his equations? How does AM radio work? Is it the same as FM radio? (No). Stay curious! |
