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

[thx1138]

Hi Folks,

Check out the Freeware Vitual analyzer http://www.sillanumsoft.org/.

I use it with my M-Tools box and it actually works quite well.

I also use Bruel & Kjar gear when.

Terry



On 4/22/13 11:41 PM, "cheater00 ." <cheater00 at gmail.com> wrote:

> 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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