Forums > MaxMSP

spectral centroid analysis

March 26, 2009 | 7:04 pm

Hello

I am wondering whether someone could give me a tip how to do a [I]spectral centroid analysis[/I], which calculates the spectral "centre of gravity" of the
signal; that is, the midpoint of its energy distribution. It is a
measure of the average frequency weighted by amplitude. This is
usually averaged over time (Miranda, 2006)

thank you
Krisztian



Ch
March 26, 2009 | 7:57 pm

Hi,

you can get a look at [centroid~] :
http://crca.ucsd.edu/~tapel/software.html

and [brigthness~] :
http://web.media.mit.edu/~tristan/

Ch.


March 26, 2009 | 8:24 pm

wonderful, thank you.
K


March 29, 2009 | 3:36 pm

Hello again

I wonder whether someone could help me here. I used the suggested objects [centroid] and [brightness] on the EEG data.
EEG data is in 120 Sampling rate.

The centroid object gives me a spectrum central of 17.2 hz which sounds good [attached picture]… but the 17.2 hz does not change at all and is the same in both hemispheres. (Live recording.)
I reckon this value should change at least a bit if I change my mind Smile, but at least when I move my eyes!

Any help greatly appreciated!!!

Krisztian

ps.: I might find something in here:
http://www.mitpressjournals.org/doi/abs/10.1162/comj.2008.32.3.87

best


March 30, 2009 | 8:09 am
tedor wrote on Sun, 29 March 2009 10:36

I wonder whether someone could help me here. I used the suggested objects [centroid] and [brightness] on the EEG data.
EEG data is in 120 Sampling rate.

Out of curiosity, wondering what hardware and communication you’re using to get and read in the EEG data? It’s an interest of mine and I’ve tinkered a bit, but haven’t found anything very satisfactory yet (in ease of use or concerning accuracy).


March 30, 2009 | 9:35 am

Hello James

I am using IBVA (bluetooth, 2ch, 3 electrode + earclip = bipolar) device. The software which came with it looks reliable. Gives me the visual representation of the raw data and the spectrum as well in 3d.

http://www.youtube.com/watch?v=MPOGguC2qgo&feature=related

I would like to use the device in Max/MSP as a biofeedback device, using a power spectrum analysis and a spectral centroid analysis.

Thank you,
Krisztian


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