[sdiy] saw vs ramp, audible?

[Eric Honour]

A lot of the discussion here is focusing on testing different waveforms -
which makes sense, as that was the original question.

But it seems to me like it's skipping a calibration step - listening to the
same waveforms *using different setups*.  Most of the differences seem like
they would depend on the characteristics of the system being used to play
the sound back; as such, I'd think there's a lot of potential for
differences to manifest based on (at a minimum) DAC, amplifier, and
speaker/headphone.

On Tue, Dec 10, 2024 at 11:01 AM Matthew Skala via Synth-diy <
synth-diy at synth-diy.org> wrote:

> On Tue, 10 Dec 2024, Roman Sowa via Synth-diy wrote:
>
> > I regret to admit that I hear the difference too. One direction seems to
> have
> > more lower end than the other. I thought maybe mp3 conversion messed up
>
> It seems to me that in order to test this properly, one should have
> objective evidence that the pressure waves really do have the same
> power spectra for sawtooth and ramp.
>
> If you use sawtooth/ramp electrical waveform -> speaker or headphones ->
> ears and the two sound different, you don't know whether that is really
> because the ears are responding differently, or the speaker or headphones
> (and other things in the chain upstream of the ears) are causing a
> difference in power spectrum and the ears are just detecting that.
>
> Instead, one should do:  sawtooth/ramp electrical waveform -> speaker or
> headphones -> microphone -> electrical waveform.  Verify that the power
> spectrum is the same for sawtooth and ramp in *that* setup, and then you
> can guess that a perceived difference is really being introduced by the
> ears.
>
> Of course this requires more pieces of good technology (in particular, the
> mic) than just going one way, but it seems to be the only way of being
> sure that the effect is really caused by the ears.
>
> On the other hand, there does seem to be abundant other evidence, and
> sound theoretical reason, to believe that identical power spectra do
> sometimes sound different to human ears when they differ by phase.  Some
> of the examples of identical power spectra in my article at:
>    https://northcoastsynthesis.com/news/do-you-really-want-that-scope/
> sound *almost* but not *absolutely* identical and it's reasonable to guess
> that that's not only because of MP3 compression or nonlinearities in the
> speakers etc.  I think one reason may be that the ears are doing envelope
> detection - for instance in my "FM versus AM" example.
>
> --
> Matthew Skala
> North Coast Synthesis Ltd.
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