# psd\_multitaper output conversion to dB (Welch)

**URL:** <https://mne.discourse.group/t/psd-multitaper-output-conversion-to-db-welch/4445>\
**Category:** Support & Discussions\
**Created:** [February 21, 2022, 12:32pm UTC](https://mne.discourse.group/t/psd-multitaper-output-conversion-to-db-welch/4445 "2022-02-21T12:32:48Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![marsman](https://yyz2.discourse-cdn.com/free1/user_avatar/mne.discourse.group/marsman/32/1206_2.png) [@marsman](https://mne.discourse.group/u/marsman)\
**Post date:** [February 21, 2022, 12:32pm UTC](https://mne.discourse.group/t/psd-multitaper-output-conversion-to-db-welch/4445/1 "2022-02-21T12:32:48Z")

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Dear experts,

I would like your expert opinion to convert values from psd\_multitaper to dB (from plot\_psd).  
Currently, I use simple conversion to dB via 10 log10 multiplication. I believe there is also a correction needed for sampling rate (2048 Hz) and from m^2 to cm^2. Still the values don’t make sense to me. The plot\_psd (from Welch) results in +30 dB for low frequencies,  
but the psd\_multitaper returns negative values for all frequency bands.

Is it possible to convert multitaper values in the range of the “Welch-values”. Perhaps anyone has dealt with this trick before, or can enlighten me. (The previous questions on the forum don’t solve this matter fully either).

Many thanks in advance!

Jan-Bernard

MNE version: 0.24.0  
Ubuntu 18.04

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<div class="post-metadata">

**Author:** ![marsman](https://yyz2.discourse-cdn.com/free1/user_avatar/mne.discourse.group/marsman/32/1206_2.png) [@marsman](https://mne.discourse.group/u/marsman)\
**Post date:** [February 21, 2022, 4:14pm UTC](https://mne.discourse.group/t/psd-multitaper-output-conversion-to-db-welch/4445/2 "2022-02-21T16:14:40Z")

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Dear reader,

I solved the question myself: For future reference It was apparently more easy than thought…  
The following conversion was needed for EEG:

psds =   
psds\_scaled = psds \* 1e6\*\*2 #V to muV^2  
psds\_scaled\_dB = (10 \* np.log10(psds\_scaled))

See also : [Confusion surrounding Epochs.plot\_psd() units · Issue #9868 · mne-tools/mne-python · GitHub](https://github.com/mne-tools/mne-python/issues/9868)