[sbagen] Binaural beat analysis

[Jim P. <ji...@ua...>]

David Tolmie wrote:
> Jim (or anyone else), can you recommend a good program for visualizing=20
> (or otherwise figuring out) the frequencies of these commercial=20
> products?  Audacity's Plot Spectrum function doesn't seem to have the=20
> resolution or go low enough in frequency to be of much use.

Remember that you are looking for the carrier frequencies (not the
beat frequencies) in the frequency analysis display -- so it doesn't
have to go too low.  However, you do need a lot of precision on the
frequency axis because even +/- 1Hz isn't much good when you are
perhaps looking at a 4Hz difference or less.

I did look into this, to see if I could pre-process an audio file so
that the binaural frequencies could be displayed obviously on analysis
software like this, but it is really complex to emulate on a computer
exactly what the brain is doing when combining the two channels.  I
got some results eventually, but it really wasn't worth pushing this
much further.  Here is the one interesting frame out of a large set of
uninteresting ones:

  http://uazu.net/temp/dive-beats.gif

For my own more accurate analysis of various recordings, I used a
simple frequency display program (e.g. equivalent to something like
the "Spectrum Display" option of a WAV-editor or whatever) to look for
the carrier frequencies in use for the binaural tones, and then I
wrote some Linux command-line software to analyse the interesting
frequency range in much greater detail.  This software is rather
improvised and unpolished, though.  It needs to be given a narrow
range of frequencies to look at, but it can give very accurate
results.

I've only used it on Linux (although I'm sure it could be ported
easily enough to Windows using MinGW or Cygwin, or built on OSX).
I've just added it to the main SBaGen page below for anyone who wants
to experiment with this.  See the README in the archive for more
details:

  http://uazu.net/sbagen/#dl_ba

Here is some example output (one output line per second):

  00:00.99 124.5+10.1/0: Left 129.6Hz (0.368842), Right 119.5Hz (0.261393=
)
  00:01.99 124.6+10.1/4: Left 129.7Hz (4.90226), Right 119.6Hz (3.63307)
  00:02.99 124.7+10.0/10: Left 129.7Hz (12.1171), Right 119.7Hz (10.3686)
  00:03.99 124.7+10.0/16: Left 129.7Hz (17.3014), Right 119.7Hz (15.581)
  00:04.99 124.7+10.0/18: Left 129.7Hz (21.718), Right 119.7Hz (18.2456)
  00:05.99 124.7+10.0/22: Left 129.7Hz (26.6568), Right 119.7Hz (22.3527)
  00:06.99 124.7+10.0/28: Left 129.7Hz (30.8397), Right 119.7Hz (27.8298)
  00:07.99 124.7+10.0/31: Left 129.7Hz (35.8012), Right 119.7Hz (31.3836)
  00:08.99 124.7+10.0/36: Left 129.7Hz (41.9454), Right 119.7Hz (35.9833)
  00:09.99 124.7+10.0/42: Left 129.7Hz (48.6545), Right 119.7Hz (41.9094)
  00:10.99 124.7+10.0/48: Left 129.7Hz (55.5671), Right 119.7Hz (47.5193)
  00:11.99 124.7+10.0/52: Left 129.7Hz (61.1117), Right 119.7Hz (51.6434)
  00:12.99 124.7+10.0/57: Left 129.7Hz (65.9308), Right 119.7Hz (56.6696)
  00:13.99 124.7+10.0/62: Left 129.7Hz (68.7725), Right 119.7Hz (61.5965)
  00:14.99 124.7+10.0/63: Left 129.7Hz (71.299), Right 119.7Hz (62.8399)

Jim

P.S.  To whoever asked, SBaGen is meant to stand for "Sequenced
BinAural beat GENerator".  Before that came 'qbagen' (quick binaural
beat generator, something like the "sbagen -i" option).

--=20
 Jim Peters                  (_)/=3D\~/_(_)                 ji...@ua...
                          (_)  /=3D\  ~/_  (_)
 Uaz=FA                  (_)    /=3D\    ~/_    (_)                http:/=
/
 Brighton, UK       (_) ____ /=3D\ ____ ~/_ ____ (_)            uazu.net

 SBaGen: binaural beats for brainwave entrainment:  http://uazu.net/SB