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 Forum index » Discussion » Composition
A fun experiment
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robsol
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PostPosted: Sun May 10, 2009 6:57 am    Post subject: A fun experiment Reply with quote  Mark this post and the followings unread

I worked on this one a few years ago, but decided that I needed more data. This is what I did yesterday:

This site: http://resource.npl.co.uk/pressure/pressure.html, contains historical data from a barometer in Teddington, UK, just outside of London. You can define the time span that you want the data from so I took the last 8 years (April 2001 - May 2009)and got the raw data from it. I stripped the dates from the text in MS Excel and fed it into Adobe Audition, where I did a DC removal and amplified it by about 45 dB, then cut the subsonics.

My wav file is about 8 seconds long, roughly corresponding to 8 years of pressure changes, and you can hear the distinct changes over a single year. If you count the repetitions, you get eight of them.

There are some clicks in there which is probably my fault (Excel will only load about 16300 rows at a time, so I had to chop he data up and do it piece by piece), but the steady tones you can hear are a mystery to me...

The thought behind this is that barometric changes and sound are the same - pressure changes over time. One is just a little slower than the other. Smile


8years.wav
 Description:
Wav file containing eight years of barometric pressure changes in Teddington, UK

Download
 Filename:  8years.wav
 Filesize:  696.83 KB
 Downloaded:  349 Time(s)


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seraph
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PostPosted: Sun May 10, 2009 7:20 am    Post subject: Reply with quote  Mark this post and the followings unread

the idea is startling, the results less so Shocked but...........it's only a start Wink
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Politics is the entertainment division of the military industrial complex - Frank Zappa
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robsol
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PostPosted: Sun May 10, 2009 7:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah, who would have thought that the weather sounds like wind in a mic? Razz
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ark



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PostPosted: Sun May 10, 2009 8:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, they're both fractal...
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Blue Hell
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PostPosted: Sun May 10, 2009 9:55 am    Post subject: Re: A fun experiment Reply with quote  Mark this post and the followings unread

Muied Lumens wrote:
I stripped the dates from the text in MS Excel and fed it into Adobe Audition, where I did a DC removal and amplified it by about 45 dB, then cut the subsonics.


Did you feed a text file to Audition or did you make it binary first?

I'm asking as I repeated the experiment and get a different outcome ;-)


baromhist.wav
 Description:

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 Filename:  baromhist.wav
 Filesize:  1.58 MB
 Downloaded:  542 Time(s)


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Jan
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Blue Hell
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PostPosted: Sun May 10, 2009 11:10 am    Post subject: Reply with quote  Mark this post and the followings unread

As in that the days are audible as a tone of about 153 Hz.
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Jan
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robsol
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PostPosted: Sun May 10, 2009 11:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
As in that the days are audible as a tone of about 153 Hz.

Of course! That sounds plausible.

I stripped off the date and time data before I fed it straight into audition. Because of the way I did it, I'm not surprised you got a different result.

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seraph
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PostPosted: Sun May 10, 2009 11:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Jan
yours sounds different because you are located in the Netherlands. I can hear the rain from here Exclamation
You don't need a Ph.D to understand something this simple Exclamation Wink

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Politics is the entertainment division of the military industrial complex - Frank Zappa
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Blue Hell
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PostPosted: Sun May 10, 2009 12:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Muied Lumens wrote:
I stripped off the date and time data before I fed it straight into audition. Because of the way I did it, I'm not surprised you got a different result.


I stripped the dates off as well and then I ran this code on it to make a binary file that I read into cool edit.

Code:
const

  in_file_name  = 'X:\Temp\baromhist.txt';
  out_file_name = 'X:\Temp\baromhist.bin';

var

  Data : array of Integer;
  AvgN : Int64;

  procedure ReadData( const aFileName: string);
  var
    aFile : TextFile;
    S     : string;
    i     : Integer;
    p     : Integer;
    N     : Integer;
    sum   : Int64;
  begin
    AssignFile( aFile, aFileName);
    Reset( aFile);
    AvgN := 0;
    sum  := 0;
    SetLength( Data, 1024);
    p := 0;
    try
      while not Eof( aFile)
      do begin
        ReadLn( aFile, S);
        N := StrToIntDef( S, -1);
        if N >= 0
        then begin
          sum  := sum + N;
          if p >= Length( Data)
          then SetLength( Data, Length( Data) + 1024);
          Data[ p] := N;
          Inc( p);
        end;
      end;
      SetLength( Data, p);
      AvGN := sum div p;
      for i := 0 to Length( Data) - 1
      do Data[ i] := ( Data[ i] - AvgN) ;
    finally
      CloseFile( aFile);
    end;
  end;


  procedure WriteData( const aFileName: string);
  var
    aFile : file of SmallInt;
    i     : Integer;
  begin
    AssignFile( aFile, aFileName);
    Rewrite( aFile);
    try
      for i := 0 to Length( Data) - 1
      do Write( aFile, Data[ i]);
    finally
      CloseFile( aFile);
    end;
  end;

  procedure DoIt;
  begin
    ReadData( in_file_name);
    WriteData( out_file_name);
  end;


procedure TForm1.BitBtnDoItClick(Sender: TObject);
begin
  DoIt;
end;

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Jan
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Blue Hell
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PostPosted: Sun May 10, 2009 12:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

seraph wrote:
You don't need a Ph.D to understand something this simple Exclamation Wink


hmm .. maybe you do ... Shocked

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Jan
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robsol
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PostPosted: Sun May 10, 2009 12:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

Jan, I'm assuming that you normalised and DC corrected the data, but I'm not a programmer, so I can't tell much from looking at your code.

I did that in Excel, using a small collection by taking the average and converting the numbers to positive and negative values. I also checked the graphs from the NPL site to see that it corresponded with the wave in AA. As far as I could see, it correlated well enough for my unscientific purpose...

Yours sound better though. Smile

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PostPosted: Sun May 10, 2009 12:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

Muied Lumens wrote:
Jan, I'm assuming that you normalised and DC corrected the data


I subtracted the average value from each data sample to remove the DC component, but didn't normalize ... I meant to do it, but there was a reasonable amount of signal, so I just later normalized in Cool Edit to -3 dB.

The biggest difference is that I saved the file as binary data, where you saved it as text probably ... but then your wave would have looked very different from the graph on the site ... so I don't quite get that bit Wink

Anyway, I checked my wave against the plot on the site as well, and thought it to look similar.

Oh there is an interpretation detail .. I set it to read data as if it were 16 bit mono PCM, your file is shorter, so probably you imported it with other settings.

Edit : I took the dots out of the data, effectively multiplying by 100.

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robsol
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PostPosted: Sun May 10, 2009 3:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

I did import a text file indeed, and was a little unsure of how the commas would be interpreted by the software, 16 bit 44.1 kHz mono. The general trend is the same as the plot, but I guess yours is much more accurate in the detail. The reason mine is a smaller file is because I pitched it up to correspond with a second a year. I conveniently forgot to mention this earlier. Wink

You did it the proper way, so I trust your judgement. I've got to learn myself how to do some of that fancy code. Very Happy

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PostPosted: Sun May 10, 2009 3:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Muied Lumens wrote:
I've got to learn myself how to do some of that fancy code. :D


Copy it ;-) (using Free Pascal and Lazarus)

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Rykhaard



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PostPosted: Sun May 10, 2009 3:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
Muied Lumens wrote:
I've got to learn myself how to do some of that fancy code. Very Happy


Copy it Wink (using Free Pascal and Lazarus)


The code minorly stumped me in formatting here and there but then, I'm just used to various forms of Basic (with a bare smattering of C and C++ and a few glances at 8 bit Assembler) over the years. Surprised

And who's this Lazarus guy, anyways? Wink
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PostPosted: Fri May 15, 2009 7:40 am    Post subject: Reply with quote  Mark this post and the followings unread

I vaguely remember reading that a telecom twisted pair cable buried underground in North America has an impedance variation which is roughly sinusoidal. I think it was due to winter/summer temperature variation.
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robsol
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PostPosted: Wed May 20, 2009 9:33 am    Post subject: Reply with quote  Mark this post and the followings unread

When looking for plugins for a friend, I came across this:

http://arvidtp.net/sw/maestro_frankenstein.php

Seems like somebody out there has similar ideas...

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