Wikipedia:Reference desk/Archives/Science/2019 July 10

= July 10 =

High Frequency Distortion Effect
Does anyone know the name of the strange effect that is observed when I play extremely high notes on a musical synthesizer? Basically, when I play an extremely high note, I get an unusually low frequency distortion noise. Also, when I use the pitch bend wheel, the normal effect is to create a simple change in pitch. However, when I do this with extremely high frequency notes, I get a rather unusual effect, which I can only describe as being similar to the rather cliched "radio tuning" sound effect, that is to say the noise you often hear in cartoons and the like when a radio is being tuned. This effect contains some surprisingly low frequencies, and has a sort of "wob-wob" sound to it.

What is the name of this effect, and why does it happen? I have searched the internet and could not find an answer for this question. do any of you know what it might be?

Could somebody please answer this question. The effect I'm looking for has been bugging me for ages now. It is known to effect frequencies of over 10,000 Hz, with frequencies of over 16,000 Hz being particular prominent in this regard. Please can I have an answer as soon as possible!? Thank you. Pablothepenguin (talk) 23:37, 10 July 2019 (UTC)

---Moved from ent ref desk:

Does anyone know the name of the strange effect that is observed when I play extremely high notes on a musical synthesizer? Basically, when I play an extremely high note, I get an unusually low frequency distortion noise. Also, when I use the pitch bend wheel, the normal effect is to create a simple change in pitch. However, when I do this with extremely high frequency notes, I get a rather unusual effect, which I can only describe as being similar to the rather cliched "radio tuning" sound effect, that is to say the noise you often hear in cartoons and the like when a radio is being tuned. This effect contains some surprisingly low frequencies, and has a sort of "wob-wob" sound to it.

What is the name of this effect, and why does it happen? I have searched the internet and could not find an answer for this question. do any of you know what it might be? 92.19.204.231 (talk) 13:13, 9 July 2019 (UTC).
 * Could somebody please answer this question. The effect I'm looking for has been bugging me for ages now. It is known to effect frequencies of over 10,000 Hz, with frequencies of over 16,000 Hz being particular prominent in this regard. Please can I have an answer as soon as possible!? Thank you. 92.19.204.231 (talk) 13:01, 10 July 2019 (UTC)


 * I believe its a form of harmonic distortion/resonance, but can't find appropriate references. Try over at WP:Reference desk/Science, perhaps(?) 2606:A000:1126:28D:84CB:D08E:899F:D254 (talk) 16:30, 10 July 2019 (UTC)  — Preceding unsigned comment added by Baseball Bugs (talk • contribs)


 * One possibility along that line is that what is perceived as a single high frequency note is actually a low note and the high note (and perhaps many in between). According to our article on harmonics: "Most acoustic instruments emit complex tones containing many individual partials (component simple tones or sinusoidal waves), but the untrained human ear typically does not perceive those partials as separate phenomena. Rather, a musical note is perceived as one sound, the quality or timbre of that sound being a result of the relative strengths of the individual partials." So, the synthesizer may be using the same method, only the low frequency notes cause resonance, and are therefore magnified to the point where they are audible and also cause distortion. Although distortion may not be the whole story, as I imagine there's a loose connection and that the low frequency causes it vibrate into and out of contact, making the "tuning the radio" sounds. That's my theory, at any rate. If my theory is right, you may be able to find a loose connection and solder it down or otherwise fix the problem.SinisterLefty (talk) 00:53, 11 July 2019 (UTC)


 * Assuming that your synthesizer is digital, it could be aliasing. catslash (talk) 00:34, 11 July 2019 (UTC)


 * String resonance.--TMCk (talk) 09:50, 11 July 2019 (UTC)


 * I can indeed confirm that a digital synthesiser was being used. Pablothepenguin (talk) 10:54, 11 July 2019 (UTC)
 * I have been able to create a file demonstrating this effect. It is called [[File:Weird Audio Effect.ogg]]. I trust you will know what effect I'm talking about now, then. Pablothepenguin (talk) 11:25, 11 July 2019 (UTC)


 * OK, that's a continuously changing frequency, like a slide whistle. All I can say is that the synthesizer is malfunctioning. SinisterLefty (talk) 14:24, 11 July 2019 (UTC)
 * I can assure you, the synthesizer is functioning correctly, it is a virtual synthesizer, so it doesn't have any actual cables. Also, sorry for using this IP Address repeatedly, I sometimes have to edit from a different device that I don't have my account on. 92.19.204.231 (talk) 17:01, 11 July 2019 (UTC), also known as pablothepenguin.


 * It may be otherwise functioning properly, but this sure doesn't sound like what it should do. SinisterLefty (talk) 20:34, 11 July 2019 (UTC)

Moiré phase resonance -- as demonstrated here: https: // youtu.be/Ql3nMG4EDrI ←[remove spaces] —107.15.157.44 (talk) 21:00, 11 July 2019 (UTC)
 * Could somebody please explain this effect to me in layman's terms? I would like to know what causes it and why only extremely high frequencies are affected. 92.19.204.231 (talk) 21:35, 11 July 2019 (UTC)
 * Actually, I don't think that video is quite right, my phenomenon concerns extremely high frequencies of over 10,000hz. Also, my phenomenon sounds a little bit like a dentist's drill. 92.19.204.231 (talk) 22:04, 11 July 2019 (UTC)


 * That effect in the video is done intentionally, of course. Tinkering with the knobs would presumably give a better example of your problem. In your situation, somehow two signals generate interferrence; I suspect the 2nd signal is a harmonic of the primary -- and the phase relationship has become unstable ... or something like that.  This creates a waveform somewhat analogous to the animation shown in the  Moiré pattern article (see right).  Imagine that the stripes in the pattern represent the high frequency crests/troughs in a waveform, and the resulting pattern represents the "wob-wob" effect. Sorta?  —107.15.157.44 (talk) 22:48, 11 July 2019 (UTC)

See Beat (acoustics). 173.228.123.207 (talk) 07:56, 12 July 2019 (UTC)
 * I am rather pleased to report that I have just ran some experiments and tests on Audacity. It would appear from my analysis that the effect in question is mostly do with a concept called Aliasing. This leads to the above mentioned Moiré effect. During my tests, I experimented with a quantity known as the sample rate. The way sample rate works is simple: the sample rate is simply the number of samples per second of audio. An audio programme such as Audacity takes audio level readings many times a second, and records the amplitude at each sample. This information is used to reconstruct the audio for digital playback.
 * My first experiments concerned pure sine waves. These are just pure frequencies with only the fundamental frequency and no additional harmonics. The sine waves were generated at 10,000 Hz and other nearby frequencies. I first played a 10,000 Hz sine wave together with a 10,100 Hz wave and notes the low beating effect, which produced a 200 Hz resultant frequency. Beating, of course, occurs when two similar but not quite the same frequencies are played together. The frequencies continually move in and out of phase, and selectively develop strong and weak points as a result. The strong points occur when the waves are in phase, and the weak points occur when the waves are offset by 180 degrees or pi radians. Usually with lower frequencies, the beating can be heard as a rather pronounced "wob-wob" effect. This effect is quite common, and can be heard with chorus effects and out of tune instruments. If the frequencies are high enough, or have an unusually high difference between them, then the beating get to a high frequency to have a definite pitch, as with the example above. I also created a sweep which played over 5 seconds, and went from 8,000 Hz to 12,000 Hz. This gave a reasonable pure sound.
 * I then proceeded to experiment with Sawtooth waves, which contain a very large number of harmonics. I repeated the experiments from above, and noted that the sawtooth wave sweep, again from 8,000 Hz to 12,000 Hz over 5 seconds, contained the effect that I asked about above. I repeated these experiments with sample rates of 44,100 Hz, 32,000 Hz and 384,000 Hz. I noted that the highest frequency you can generate for a particular sample rate is equal to half of that sample rate. I also noted that the weird effect was much less pronounced with the 384,000 Hz sample rate. Finally, I noted that the weird effect had a particular resonance at exact fractions of the sample rate frequency. 92.19.204.231 (talk) 15:00, 12 July 2019 (UTC)