#1
SMART PEOPLE: I've never heard of this being done, so help me out, and try to stick with me as I try to explain. I'm trying to make a technique to make a stereo signal sound like it's revolving around you... without changing the amplitude. Don't tell me it can't be done, because you're basically going to reproduce how it would sound to be listening to a speaker while spinning in circles, or while an audio source was revolving around you.

We all know how to make a sound that revolves around you're ears using the amplitude of the signal. So with my idea, you'd need to change the timing at which the signal hit your ears to create this effect. Essentially, you'd be constantly shifting the signals timing by small amounts. Here's where the Doppler effect comes in. At one point in time, the L signal will be x amount of time from the R signal. Then they'll move in relation to each other so that L and R will be at the same time (x = 0). Essentially, the tracks will be speeding up and slowing down at regular intervals which would change the pitch, and cause audio gaps, and "pops". Can you help me code an effect (like for reaper or audacity) that handles this. If not, just let me know what you think.
#2
My first question would be what use you have for this effect, and why you want to use it. What sound will it be applied to? I'm guessing a guitar, but what kind of guitar sound?
#3
are you talking about like rotating speakers? im pretty sure that theres like effect pedals that have that sound to em.. i dunno if thats what your talking about
#4
well, honestly I want to do it just because. I think it'd be a neat effect, and the whole "doppler" effect thing may have some interesting effects on widening the sound because a recording at say 440hz, will sound more like 439 to one ear, and 441 to the other, but constantly be changing, if you understand the whole principle this thing is based on. It'd also sound truer to how a rotating effect would be in real life. I really don't know how to code stuff in audio languages, so I'd need help (or someone to do it for me ).

If anyone understands the "Head Related Transfer Function", that knowledge may help. If there's any program for using the HRTF in audio files, that'd be real easy.

Thanks again.
#5
Maybe with some hi-tech pan, its possible. I mean, whats the point of surround sound, if you can only utilize left and right.
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#7
You people dont understand what he is asking I think. A rotary speaker is a rotating speaker, so you hear the doppler effect, but also the volume fluctuates with the directivity of the horn. He wants the effect that a single speaker, pointed at you, rotated around YOU. The level doesn't fluctuate, but the location does.
#8
you can move the speaker closer and farther away while recording which will help produce the dopler effect. I'm not sure what exactly your asking but i think this is it.
#9
so youre saying detuning the pitch slightly, and varying it from ear to ear?
You could pay some hobo to detune your strings while youre paying if you wanted.
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#10
Set up two amplifiers pointed towards a microphone sitting on a lazy susan?
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#11
this is an interesting question, but idk if it would sound like it is going "around" you so much as past you, i mean due to the frequency variation.

well the more i think about i guess it could be possible. it would have to be perfect tho, it would take forever to get right i think, the frequecy change and the panning would have to hit like perfectly.....ohhhh tough
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#12
http://www.youtube.com/watch?v=IUDTlvagjJA

It can be done by placing several microphones on different places and recording while moving around the mics. Its called holophonics. Although it works together with signal amplitude it also has to do with the timing at which the music gets to your ears.

Was this what you meant?


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#13
that actually sounds like an inaccurate discription of the doppler effect, at least as i understand it. the doppler effect basicly is that as something approaches you, the pitch gets higher, and as it moves away it gets lower. so unless you want something to be lower pitched in one ear and higher in the other, then go to unity, then back, it wouldnt really work. varying the time it hits your ears wouldnt really be practical, i would still say that messing with the amplitude would be the easiest way to do it.
#15
First off, thanks for the replies, but half of you don't get it (no offense meant, I explained it poorly)

A few people mentioned analog ways of doing it by moving around a speaker, and yeah, that'
s pretty much what I'm talking about. And the holophonics, yeah it's all similair to that, but I want a way to reproduce it digitally so you can play with the "speed of rotation" and other such aspects.

Let my try again to explain what I'm talking about. If you wanted a sound to stereoscopically move around your head without changing the amplitude experienced by either ear, you'd have to change the time difference between when a sound hit the ear. So lets use just the left ear for a reference right now, and we'll talk about it as if a speaker were moving around the head, but in reality it'll just be the "digital location" of where the source sounds like it's coming from.

So you have a left ear, and a speaker that's rotating from an axis between the left and right ears. When the speaker is to your right, the speaker is further from the left ear than when the speaker is on the left side. So let's say the speaker is rotating clockwise around you as viewed from above. When the speaker is moving in front of you, it's also travelling further from the left ear, and therefore the pitch will drop a small amount. When it's moving behind you, it'll be moving towards your left ear, so the pitch will raise a little bit. That's all I mean by the doppler effect.

So do recreate this, you'd have to speed up, and slow down different parts of each channel, and they'd be opposite from eachother, so while one's speeding up, the other is slowing down, and they trade off in a circular fashion. It would be alot like using a holophonic dummy head spinning around, but I'm kind of wanting to find a way to make holophonic sounds on a computer for a little finer control.

Any thoughts? THanks for feedback!
#16
Very cool idea. I'd be interested to see how you go with this project. If I wasn't so flat out at the moment I'd be keen to get involved. I'm a programmer by trade.. I haven't done much with DSP, but I would like to. Anyway, good luck and keep us updated
#17
I'll admit I don't know much about DSP, though there are probably forums around for that - they may have examples of such a thing. My way of doing it is to use an eventide - that way I can do the same thing live in small-medium venues. I use four preamps with four signal paths through effects like chorus/flanger, so the eventide takes quadraphonic input. You could have just one preamp, and use the algorithm to move it around, left and right, front and back. I can take it further by doing the same for all four preamp inputs, or two guitar and two keyboard, so each one is moved around in space at the same time. Problem is, in large venues the time delay makes it less effective - you just hear a simple panning, instead of the illusion of having these sounds moving around your head, so I have a set of presets that use just stereo imaging instead.
Still, it can be done. Doing it on a recording would be more effective because the listener is close to the speakers/headphones.
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#18
I perfectly understood what you meant, and yes indeed its a cool idea.... but its very complicated, maybe you should search for an audacity forum or something like that, or even try to contact the creators of some of the effects plugins. I personally have no idea of how to do it, but if you are able to do it sometime, let me know.


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#19
I think i know what you mean. Adobe audition has it so it sounds like surround sound but only out of two speakers. is that what your trying to do? if so its called Stereo Field Rotate.