Overnightscape Central – Midsummer Madness (8/5/13)
Podcast: Play in new window | Download
1:42:01 – It’s MADNESS!! Â Carrie Michel, Geoff Sink, and Frank Edward Nora join a brain-melted PQ Ribber for this weeks collaborative creation!
Next: Radio Graffitti
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 United States License.
Overall attribution by PQ Ribber , all other hosts appear courtesy of themselves.
Released August 2013 on The Overnightscape Underground (onsug.com), an Internet talk radio channel focusing on a freeform monologue style, with diverse and fascinating hosts presenting  an array of talk-driven programs that are inspired by the Magic of the Human Voice!
Beings of Frequency http://www.youtube.com/watch?v=IF_rorl5LRQ
Comment by Eddie — August 6, 2013 @ 10:04 am
A nicely worded description of how a single vibrating speaker can produce so many unique sounds at once:
. . . . how is it that a system with only one output (the physical driver/cone), only capable of vibrating at a single specific frequency at one moment in time . . . .
No no no. Your problem is not in understanding how loudspeakers work; it’s in understanding how sound works.
The sound you hear is the result of nerve endings in your ears reacting to the vibration of the tissue in which they reside; then converting that kinetic energy into electrical impulses; which then go to an area in your brain for decoding. It’s fairly similar to your sense of touch, which is sensitivity to pressure, but it’s decoded by your brain in a much different way.
That tissue vibrates because the air molecules adjacent to it are vibrating. (Or water molecules, if you happen to be swimming underwater.) Your question could be just as easily restated as: “How can a molecule produce different sounds simultaneously by vibrating at a single specific frequency at one moment in time?”
The answer is: It does not vibrate at a single frequency.
It would help you understand this if you know someone who can take you into a sound studio and show you sound waves on an oscilloscope. You will see that “sound” is not a nice clean sine wave with an easily visible frequency and amplitude. It’s an incredibly complicated waveform: the mathematical sum of all the individual sounds that are picked up by the microphone.
If it’s music you’ll see a repeating pattern, although the shape of the wave may be so complex that the repetition might be difficult to spot. If it’s conversation or ambient noise there won’t be a repeating pattern, because the individual component waveforms don’t have regular repeating shapes, i.e., they’re not music.
Consider the way you tune a guitar. (I play bass guitar but it works the same way.) You finger the E string on the fifth fret and pluck it so it produces an A, at the same time plucking the open A string. If the instrument is in tune both strings produce the identical note and you hear an A — air vibrating at 440Hz. But if the strings are slightly out of tune, one is vibrating at (say) 440Hz while the other is at (say) 432Hz.
If you capture this with a microphone and look at the waveform on an oscilloscope, you’ll see a wave that is the sum of a 440Hz function and a 432Hz function. It will look somewhat like a note with the frequency of 436Hz (a slightly flat A), but with the amplitude slowly changing from one wavecrest to another. If you pan out the scale of the display so you can see several pulses at once, you’ll see that the amplitude changes at a regular interval of 8Hz and the combined wave is perfectly regular, but more complicated than a single note.
And the reason I use this example is that you can hear this waveform. This is how we old-timers tune our instruments. (We didn’t have these newfangled digital tuners, which IMHO are useless crap anyway). If you pluck two strings simultaneously that are an A note but 8Hz out of synch, you will hear an A, but you will clearly hear the amplitude (loudness) of the note increasing and decreasing at 8Hz (8 times per second). We call those “beats.” Of course if the beats are much faster than 15-20 per second we can no longer discern them, and instead of hearing beats we just hear dissonance. If the strings are that far out of tune (after all, if the frequency drops to 411Hz, a mere 29Hz out of tune, it’s reached the pitch of a genuine A-flat) we can hear the difference and get them closer by turning the pegs a little bit, then plucking them again and listening for the beats. Eventually we get them to the point that there are no beats and the strings are vibrating in unison, i.e., they are perfectly in tune.
The molecules in the air are doing exactly the same thing the cursor on the oscilloscope is doing, which is exactly the same thing your eardrums are doing, which is exactly the same thing the microphone is doing, which is exactly the same thing the loudspeakers are doing: Adding the individual sound waves mathematically to vibrate in one single but very complicated waveform.
Throughout this chain of events, from the moment two sounds are created in the same physical location all the way through the recording, playback and listening process, the molecules in the air, equipment, or your body are not “vibrating at a single frequency.”
No precision is lost in this process. The molecules in the air, the microphone and the loudspeaker are capable of vibrating at frequencies up into the millions of Hz, easily adding sounds together and sending the aggregate waveform to your ears for your brain to deconstruct.
The grooves in an old vinyl record, under a microscope, look exactly like the sound waves on the oscilloscope. Like the air, microphone, loudspeakers and eardrums, the phonograph needle is also well able to vibrate in a complicated pattern that combines multiple frequencies of sound into a single waveform–reproducing sounds up into the high frequencies and down into the bass range that you can’t hear. The same is true of magnetic recording tape and radio waves.
Digital recording media, of course, do not have quite this degree of precision. CDs can’t match the sound quality of a brand-new vinyl LP or a 32-track studio tape, although the drop-off is very slight. For most of us the difference is–literally–inaudible, but some people, especially fans of symphonic music with its much greater loud-to-soft range than pop music, claim that they can hear it.
People who listen to their music on cellphones can’t possibly hear the difference and those people really don’t care anyway.
Comment by chad bowers — August 6, 2013 @ 1:29 pm
Eddie: that video confirms why I have no phone of my own and my work phone is wired into the wall. Im sure the wi-fi signals i bathe in make up for this, though….
Chad: i thank goodness, itself for electronic tuning aids… maybe its that i use an open tuning, but they seem to work better for me…
Comment by pqribber — August 6, 2013 @ 1:59 pm
Chad, this audio thing reminds me of my struggles to really understand what is going on in holography. I get a lot of the observations about what is going on but:
In holography, you have a clear gelatinous substance with dark flecks in it – how can this possible produce a 3D image, and not only that, when the hologram is broken apart, each part has the complete image. Again – dark flecks in clear gelatin – I just don’t get how that can make the 3D image.
In audio, it’s a single vibration, in-out, and yet somehow this makes all these overlapping sounds. I get some of the math involved, but again, there is, to me, a disconnect, in this one in-out vibration being able to produce a vast, complex, multi-layered sound experience.
I’m sure there is an answer, and I suppose some people may actually understand it. But I just don’t get it.
just imagine the surface of a pool of water, with multiple ducks swimming and disturbing the water, all those outspreading concentric waves, intersecting and interfering with each other. At any one point in the water, the water is just going up and down. Yet in these theories, that single up and down contains all the information of all the sources of all the ripples. To me, it seems that singe point of water going up and down would just be a scrambled mess, all the waves coming from all these directions, just static. But in this case, clearly, my intuition is wrong, and I can’t see why it’s wrong.
Comment by Frank — August 7, 2013 @ 7:20 am
I know what you mean. I find it interesting that we can make draw holograms using a simple trick: http://amasci.com/amateur/holo1.html
for me the part that makes the audio make sense is that you are recording the vibrations as heard in one location, wherever the mic is, and you are then playing those vibrations from a speaker, so it is a clever work around to having to actually remap the full dynamic action of a room full of sounds.
In other words if you truly recorded the entirety of what was happening, you could then wander around inside the soundfield and experience it from different positions and heights, and distances through the room.
But with the audio recording we are limited to just what was captured in that one location.
If we record form a speaker on the right and the left, we can recreate some of the dimensionality of the room but not the real life experience of it.
–
I think in holography it is a similar “cheat” going on. You start with a laser, which is convenient because it is coherent and not just scattered like normal light, then you bounce that laser over an object, the hologram material just captures the reflections of that coherent light.
I need to try this: http://amasci.com/amateur/holo1.html , it seems like in these hand drawn holos, the compass is taking the place of the laser, representing the arced field of view through its drawn interference patterns.
Comment by chad bowers — August 9, 2013 @ 8:31 am