How is voice sound on TV or phone distorted through a face mask?
There are many researches on the acoustic effect of masks since the pandemic. You can find them on the website of The Journal of the Acoustical Society of America and most of them are free to access.
Masks have selectivity on both frequency and spatial.
In frequency domain, masks react as low-pass filters that attenuate high frequencies significantly. Interestingly, different research gives different results. They are saying 1 kHz$^{[1]}$, 2 kHz$^{[2]}$ and 3 kHz$^{[3]}$ maybe due to different understanding about &quot;significantly&quot;.
In spatial domain, masks lead to reduced frontal sound radiation compared to the lateral or rear radiation at high frequencies$^{[2]}$.
Researchers also tested the effect of microphone placement. They placed microphones on the lapel, cheek, forehead, and next to the mouth$^{[1]}$. These differences are mostly caused by the spatial radiation pattern with a mask.
And of course, different masks have different acoustic effect according to their materials, weaves and types.
References

[1] Acoustic effects of medical, cloth, and transparent face masks on speech signals
[2] Impact of face masks on voice radiation
[3] Effects of face masks on acoustic analysis and speech perception: Implications for peri-pandemic protocols
[4] Acoustic effects of non-transparent and transparent face coverings

[5] Effect of masks on speech intelligibility in auralized classrooms