[sdiy] Audio test generator and mesurement tool - can anyone suggest a good set?

[cheater00 .]

Thanks for the reminder about the weird nature of hearing. It's good
to have that every now and then.

But no, this is mostly just so that I have a tuneable oscillator that
goes below 20 Hz, that's all.

On Tue, Apr 23, 2013 at 3:01 AM,  <rsdio at sounds.wa.com> wrote:
> On Apr 22, 2013, at 10:07, cheater00 . wrote:
>>
>> Also: are distortion analyzers usually limited to 20 Hz - 20 kHz, or
>> are there ones that go below 1Hz and high above?
>
>
>
> I just attended an Audio Engineering Society talk/lecture titled "Audio,
> Radio, Acoustics, Signal Processing—the Way Forward," by J.J. Johnston,
> where a very important point was made: noise measurements are completely
> meaningless unless the spectrum is considered (i.e. SNR is pointless w/o
> spectrum). That's because our hearing is very frequency dependent, and
> signal-to-noise ratios as poor as 6 dB can be fine because the noise
> (distortion) is inaudible. Meanwhile, a 60 dB signal-to-noise ratio might be
> insufficient if the harmonic distortion or other noise is at a very
> sensitive frequency like 1.5 kHz. Not all THD is the same!
>
> Distortion is basically a subset of noise, and if you can't hear the
> distortion then there's little need to measure it. Below 20 Hz, you're maybe
> going to feel something, but you can't really hear it. It's difficult to
> calculate amplitude for extremely low frequencies anyway, so I don't see the
> point of measuring distortion below 20 Hz. Any significant amount of
> harmonic distortion will involve harmonics within the 20 Hz to 20 kHz band,
> so those would be measured. Don't forget that if you're controlling the test
> signal frequency, then you can still measure the *audible* distortion from
> signals between 1 Hz and 20 Hz, but the THD factor will only include the
> harmonics we can hear.
>
> As Neil mentioned, there is certainly measurement available above 20 kHz, so
> the argument about what can be perceived above that doesn't need to be
> settled before you can measure it.
>
> Brian Willoughby
> Sound Consulting
>
>
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