How empty are the voids in the universe?

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The discussion focuses on the measured density contrast within cosmological voids, specifically those with a radius of about 30 Mpc. A referenced paper by L. da Costa indicates that the density inside these voids drops to approximately 20% of the average, resulting in a density contrast of -0.80. Participants seek more recent studies that provide actual measurements of matter density in voids, rather than simulations. They express a need for updated data that includes both visible and dark matter, as previous articles primarily address visible matter underdensity. The conversation emphasizes the importance of obtaining direct measurements to enhance understanding of cosmic voids.
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What is the current measured density contrast inside the cosmological voids of radius about 30 Mpc? By measured I mean somebody constructed a density map based on peculiar velocities map or weak lensing.

I've read a Paper by L. da Costa - Astrophysical Journal 468, L5, 1996 - that constructed a density map of our neighbourhood (radius about 100 Mpc) based on measured peculiar velocities of galaxies. According to the density contours the matter (visible and dark) density inside the voids around us drops to about 20% of the average i.e. density contrast = -0.80.

Has anyone seen more recent paper that measure the matter density in the voids?
 
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Thanks for the articles. What I had in mind though was something like an update of the article I cited since its more than 10 years old.

The first article you posted talks about N-body simmulations of dark matter - I need actual measurements not simmulations of something that hasn't been detected directly yet.

The second article talks about voids in the Sloan Digital Sky Survey but there they talk about the underdensity of galaxies in voids, i.e. underdensity of visible matter while I'm interested in the total underdensity including visible and dark matter.
 

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