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Post by Chris St'Aubyn on Apr 2, 2017 8:06:17 GMT
Hey Ethan, after doing some testing I've come across a test result I just can not seem to figure out. The test started when I asked myself if the direction of the waveform made an audible difference in a synthesizer. To test this question I generated an a SAW wave with a synth. I recorded this SAW wave to an audio track. I then took this audio track and duplicated it and reversed it. To no surprised it Nulled. This tells me that the waveform has no audible difference when flipped. The issue I have is with this next section of test. I decided to chop sections in both tracks and then have them play one after another and suddenly they sound as if they are different even though I know they are the same. Why does this happen? What is causing this? Here's an image of what I did to set up the second part of the test. One track is the regular waveform and the other is a reversed copy of the same track. I've also attached an audio sample of the test. Here's what it sounds like. It sounds the same, yet almost like it's switching tones.
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Post by Hexspa on Apr 2, 2017 11:01:45 GMT
Hey Ethan, after doing some testing I've come across a test result I just can not seem to figure out. The test started when I asked myself if the direction of the waveform made an audible difference in a synthesizer. To test this question I generated an a SAW wave with a synth. I recorded this SAW wave to an audio track. I then took this audio track and duplicated it and reversed it. To no surprised it Nulled. This tells me that the waveform has no audible difference when flipped. The issue I have is with this next section of test. I decided to chop sections in both tracks and then have them play one after another and suddenly they sound as if they are different even though I know they are the same. Why does this happen? What is causing this? Here's an image of what I did to set up the second part of the test. One track is the regular waveform and the other is a reversed copy of the same track. I've also attached an audio sample of the test. Here's what it sounds like. It sounds the same, yet almost like it's switching tones. The difference is subtle. There are two types of saw waves: ascending and descending. I think this video describes them: youtu.be/mqY6cVJS9foI forget which synth it is but one of the designs is harder to make but sounds better. When I reverse the waveform in question and play it back I don't get nulling. That only happens when I invert the polarity and keep them the same direction. -m
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Post by arnyk on Apr 2, 2017 15:08:59 GMT
Hey Ethan, after doing some testing I've come across a test result I just can not seem to figure out. The test started when I asked myself if the direction of the waveform made an audible difference in a synthesizer. To test this question I generated an a SAW wave with a synth. I recorded this SAW wave to an audio track. I then took this audio track and duplicated it and reversed it. To no surprised it Nulled. This tells me that the waveform has no audible difference when flipped. The issue I have is with this next section of test. I decided to chop sections in both tracks and then have them play one after another and suddenly they sound as if they are different even though I know they are the same. Why does this happen? What is causing this? Here's an image of what I did to set up the second part of the test. One track is the regular waveform and the other is a reversed copy of the same track. I've also attached an audio sample of the test. Here's what it sounds like. It sounds the same, yet almost like it's switching tones. The test signal has a fundamental frequency of about 262 Hz, which is below 1 KHz, and thus in the region where the ear has some sensitivity to phase. I've only listened to the track on headphones, and with headphones the ear seems to be generally more sensitive to variations in phase, probably mostly because the phase-scrambling properties of the room are vastly reduced. This is a continuous wave which has a consistent harmonic structure, both of which are generally never a property of regular music, whether recorded or live. Bottom line is that reversing the direction of playback changes the phase relationships between the fundamental and the harmonics in the test wave form, and enough of those harmonics are at a low enough frequency that they can be heard in certain listening environments. It has long been known that certain generated tones produce reliable audible identification of certain kinds of signal processing, even when that processing is difficult or impossible to hear with regular music.
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Post by Ethan Winer on Apr 4, 2017 20:48:33 GMT
I've come across a test result I just can not seem to figure out. The test started when I asked myself if the direction of the waveform made an audible difference in a synthesizer. To test this question I generated an a SAW wave with a synth. We had a large discussion about this on Facebook recently. I'm convinced that our hearing is not sensitive to phase shift unless the amount of shift is very large. What we're really hearing is due to non-linearity in either the speaker driver, our ears, or both. This short article explains in detail, and includes several audio examples: IM Distortion in the Ears
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Post by Chris St'Aubyn on Apr 8, 2017 0:34:08 GMT
Thanks. This helps put things together for me.
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