But the filtered out low frequencies will have modulated the higher frequencies of the the intended audio content. More difficult to process but the LF signal is there.

Layering false signals on top just means there’s fake locations to rule out.

And if it’s video: https://news.mit.edu/2014/algorithm-recovers-speech-from-vibrations-0804

Looks like it might be supported by OpenWrt soon: https://openwrt.org/toh/tp-link/tp-link_festa_f52-outdoor_v1

Status: Device support is proposed in OpenWrt PR #24903 and depends on firmware-utils PR #74. Neither PR has been merged at the time this draft was checked. No official OpenWrt image is linked here. Do not flash an EAP225-Outdoor image to the F52-Outdoor merely because their hardware is similar.

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Industrial-scale coffee brewing can use counter-flow heat exchangers to recover pretty much all the heat energy, combined with insulation to prevent losses.