On Sunday, November 22, 2015 at 7:22:45 AM UTC-8, Victor Reijs wrote:
> On Saturday, 21 November 2015 17:42:16 UTC, rickman wrote:
> > 404. That's an error.
> >
> > The requested URL was not found on this server. That's all we know.
>
> Don't know why you get this... I see the pictures (but that is perhaps because I am the uploader...) Are you login- into Google photo? Sorry I am not yet used how to properly use these services... Hope someone else knows why you get this 404.
>
> All the best,
>
>
> Victor
I also get 404.
Reply by Victor Reijs●November 22, 20152015-11-22
On Saturday, 21 November 2015 17:42:16 UTC, rickman wrote:
> 404. That's an error.
>
> The requested URL was not found on this server. That's all we know.
Don't know why you get this... I see the pictures (but that is perhaps because I am the uploader...) Are you login- into Google photo? Sorry I am not yet used how to properly use these services... Hope someone else knows why you get this 404.
All the best,
Victor
Hello Mark,
On Friday, 20 November 2015 20:22:34 UTC, mako...@yahoo.com wrote:
> On Friday, November 20, 2015 at 2:43:24 PM UTC-5, Victor Reijs wrote:
> Is the y axis dB below full scale?
> If so, those are pretty low levels.
It is the dB directly from Audacity's 'Frequency Analysis'. It is indeed a quite low volume (it is silence in a room).
All the three plots are of silences in the same room, but different sampling freq. and/or bit depth (and at slightly different times).
If I use the line-in without any source connected, I get this FFT Frequency Analysis (using audacity):
https://photos.google.com/search/_tra_/photo/AF1QipMW2jfVERXorlDwiakFRuCnxPwx0l-79qqvPwI_
In this case the recording level was 100 (while in the other plots it was around 45).
> The noise may be unwanted crosstalk from the digital circuits into the
> analog. If they are below the frequency range of your interest, high pass them away.
In some way, I might be interested in low frequencies, as neolithic chambers and their passages can behave as Helmholtz resonator (resonance frequency around 10 Hz). So that is why I was thinking in changing the sampling frequency or bit depth for two recordings. In that case I hope the internal recorder noise's peaks will change with the bitdepth and sampling rate, while the real sound peaks stay the same... What do you think?
> If the acoustical signals you want to study are very low level, then you may benefit from an external preamp to increase the electrical signal level before it enters your recorder. That will relatively reduce the level of this unwanted noise.
That sounds a good idea. In the case I am interested in infrasound, I just use an amplifier that has a low pass filter (say 40 Hz). Thanks for that hint!!!
All the best,
Victor
Reply by Eric Jacobsen●November 20, 20152015-11-20
On Fri, 20 Nov 2015 11:43:15 -0800 (PST), Victor Reijs
<victor.reijs@gmail.com> wrote:
>On Friday, 20 November 2015 18:57:13 UTC, Eric Jacobsen wrote:
>> On Fri, 20 Nov 2015 08:57:04 -0800 (PST), Victor Reijs
>> >How do I send a picture on this group?
>
>> You can post a file to a cloud server (dropbox, google drive, etc.,
>> etc.), or any site with public read acces, make it public and post a
>> link here.
>
>I hope this is visible:
>https://goo.gl/photos/3GP3hcoyxuSUvKqTA
Yes, that's visible.
Those don't looke like sinc sidelobes. They more closely resemble
harmonics or are perhaps some sort of processing artifact. If you
can't completely eliminate acoustic stimulus, which I'd guess is hard
to do, could that be harmonic resonance of the environment? I'm
guessing there.
Is the vertical scale dBFS? What is the reference for the dB scale?
Eric Jacobsen
Anchor Hill Communications
http://www.anchorhill.com
Reply by ●November 20, 20152015-11-20
On Friday, November 20, 2015 at 2:43:24 PM UTC-5, Victor Reijs wrote:
> On Friday, 20 November 2015 18:57:13 UTC, Eric Jacobsen wrote:
> > On Fri, 20 Nov 2015 08:57:04 -0800 (PST), Victor Reijs
> > >How do I send a picture on this group?
>
> > You can post a file to a cloud server (dropbox, google drive, etc.,
> > etc.), or any site with public read acces, make it public and post a
> > link here.
>
> I hope this is visible:
> https://goo.gl/photos/3GP3hcoyxuSUvKqTA
yes it is.
Is the y axis dB below full scale?
If so, those are pretty low levels.
What kind of recorder is it.
The noise may be unwanted crosstalk from the digtal circuits into the
analog. If they are below the frequency range of your interest, high pass them away.
If the acoustical signals you want to study are very low level, then you may benefit from an external preamp to increase the electrical signal level before it enters your recorder. That will relativly reduce the level of this unwanted noise.
Mark
Reply by Victor Reijs●November 20, 20152015-11-20
On Friday, 20 November 2015 18:57:13 UTC, Eric Jacobsen wrote:
> On Fri, 20 Nov 2015 08:57:04 -0800 (PST), Victor Reijs
> >How do I send a picture on this group?
> You can post a file to a cloud server (dropbox, google drive, etc.,
> etc.), or any site with public read acces, make it public and post a
> link here.
Reply by Eric Jacobsen●November 20, 20152015-11-20
On Fri, 20 Nov 2015 08:57:04 -0800 (PST), Victor Reijs
<victor.reijs@gmail.com> wrote:
>On Friday, 20 November 2015 16:25:38 UTC, Eric Jacobsen wrote:
>> Could you maybe post a graph of what you're seeing? If there is a
>> DC offset, even a small one, it could be sidelobes from that.
>
>How do I send a picture on this group?
>I used in Audacity Effects -> Normalize... -> 'Remove DC offset' before the analusis.
>
>I understand in MATLAB one has the function 'detrend' but that is not available in Audacity...
>
>All the best,
>
>Victor
You can post a file to a cloud server (dropbox, google drive, etc.,
etc.), or any site with public read acces, make it public and post a
link here.
Eric Jacobsen
Anchor Hill Communications
http://www.anchorhill.com