Understanding the unit of measurement used on the Chart

[giraffepigcat]

James,

The math is too hard for me But I would try to get it.
By just now I saw FTT works on how to split out different wavebands by frequency and make sure the energy remains the same.
As for PSD, it indicates the intensity or chance of wave frequency.

Maybe I did not know if I was thinking correctly in this post or last one. I don't really know any calculating process.
Back to the P1 and P0 problem, wiki says (dB) = 10 log(P1/P0) which means dB is a relative unit of measurement.
So I was curious about the absolute brainwaves including Delta, Theta, Alpha, Beta, and Gamma in dB units based on PSD.
Each frequency band has an amount of PSD. Is their any part to make each waveband into the relative form, i.e. dB unit?

[James]

Relative waves can be calculated from the absolute waves.
See: https://web.archive.org/web/20181105231 ... and_Powers

[giraffepigcat]

Sorry that I was confusing you, James.

I meant absolute brainwaves in dB. And dB is a (relative) unit-----(dB) = 10 log(P1/P0).
I wanted to know is there some process to get PSD of each waveband converted into dB?

[James]

dB is just there as a label, it has no math meaning.

[giraffepigcat]

Got it, thank you.
I have something else to ask. What for is low_freqs (2.5-6.1Hz) is recorded? It overlaps with part of Delta and Theta.

low_freqs 2.5-6.1Hz
delta_absolute 1-4Hz
theta_absolute 4-8Hz
alpha_absolute 7.5-13Hz
beta_absolute 13-30Hz
gamma_absolute 30-44Hz

[James]

I don't calculate that.

[giraffepigcat]

I see. Thank you so much for quick responses, James!

[AlbertE]

Hi James,

I hate to resurrect this discussion, but could we TECHNICALLY say that the PSD "unit" as it were, can be described as microwatts or just watts? I mean PDS is a measure of power density, right? Also, I've read that you often say the range CSV files is 1:-1, but I see values as high as 1.5. How can we explain this? I also know you've said not to think about the units, the reason I keep wanting a quantifiable unit of measure is so I can test significance of change from control trials to treatment trails. If we don't establish a unit of measure, is there another way this can be one, based on your experience? I don't want to take up a lot of your time, so if the explanation requires a dissertation, then just point me to an article and I'll take it from there. Thanks so much!

[James]

No. A Watt is a specific quantifiable energy unit and that is not what the PSD is.

The range is not limited to -1:+1. I've always stated that values are commonly in the range -1:+1. Values above and below are normal and fine.

If you want values that are of a fixed range, then use Relative Brainwaves.