Achieve good time domain behaviour to produce single cycle sine

What does it look like?

Uh, ...maybe like a single cycle 50Hz sine wave 🙄

one cycle 50Hz visual.JPG
 
No, of course not ..it's obviously the pict of the wav file i uploaded

The listening test was pretty darn conclusive.
But I'll probably still do the mic & scope test,
as much to learn how to do the necessary scope triggering, as to see how the measurement compares to the wave.

But learning that triggering may come easy or hard, sooner or later...dunno...current project..
Will post scope trace if i get it to work well.... when i feel it's real data...
 
No, of course not ..it's obviously the pict of the wav file i uploaded

The listening test was pretty darn conclusive.

Of what? Now listen to it thru a full range speaker. Notice any difference?

Look at the end of the sine where it does an instant 45 degree change. The speaker cone has to stop instantly. And start instantly at the begining. This is only possible with infinite bandwidth. Thats why these waveforms do not exist in nature.
 
Last edited:
Hi cbdb,

Yes, when i listen to it full range it gets sharper, more full spectrum.

But I'm a little suspect about the test file now...
JRiver buffers and plays it quite differently, play to play.
Didn't hear that with just the sub.
Maybe it's just too short a file to use..

I'd advise folks not to try it with anything other than a sub, or better just scrap it, till a proven file that has digital silence before and after to make sure it plays correctly.
I'm out of my element building digital soundtracks....looking forward to trying my arb generator output, when the amplifier option arrives.

When you explain why these waveforms do not exist in nature, that makes sense.
Thx ! 🙂
 
Thats why these waveforms do not exist in nature.
The naturally occurring "N" waveform of a thunderclap would have some similarity to a truncated sine wave like Mark posted.
Although I have heard the "crack" sound of randomly truncated sine waves many times when un-muting them through a good full range system, having been within 100 feet of a lightning strike two times in my life, have to say there is no sound system that has come very close to reproducing that sound.
And that's fine by me- but still wonder what the OP Wonderfulaudio application is...

Art
 

Attachments

  • N wave.png
    N wave.png
    216.1 KB · Views: 145
Last edited:
If I have understood correctly, the thesis is that a single sine wave is not actually a sine wave at all. This is because, for example, when it starts at t=0, it needs to accelerate from a velocity of zero to a finite velocity in zero time; this is infinite acceleration and it is posited that this requires an infinitely large bandwidth. A continuous sinewave, on the other hand, has the advantage of momentum to help the system achieve the velocity required at the zero crossing.

This sounds believable as a thought experiment, but if the reasoning is correct, then surely we would expect the fft of a “single sinewave cycle that is not really a sinewave at all” to show a raft of harmonics, which would be the reason it would require a large bandwidth. If the harmonics are not there, then there would be no need for the large bandwidth.

LTspice will happily perform an fft on one cycle of a 50Hz sinewave. I’ve attached a screenshot below. I can’t see any evidence of this requiring a large bandwidth. Moreover, if the output is filtered at, say, 100Hz, the single sinewave cycle will still be passed unchanged.

Since the time-domain and frequency-domain analyses are mathematically related and just different views of the same phenomena, perhaps someone here could explain to me how this relationship is apparently broken in the case of a single sinewave cycle.
 

Attachments

  • Capture.PNG
    Capture.PNG
    90.5 KB · Views: 130
Good question.

Capture1.png is the fft over the time period of the single cycle only.

Capture2.png is the fft over the whole of the time period, i.e. with silence before and after included in the fft.

Not quite sure what to make of that!
 

Attachments

  • Capture1.PNG
    Capture1.PNG
    92.4 KB · Views: 128
  • Capture2.PNG
    Capture2.PNG
    90.6 KB · Views: 131