One of my biggest pet peeves is not being able to hear the dialogue of a movie or TV show because some sort of background noise is drowning it out. I was able to partially solve this by turning off my air purifier when the TV is playing media.
Most of the background noise is either my furnace kicking on or my Levoit Core 400S air purifier running in the background. The latter pretty easy to automate with the formatBCE/HA_VeSync_Classic300s modification to the VeSync integration. This alteration to the integration adds more device support including my air purifier.
You'll also need some sort of media player added to Home Assistant. I watch almost everything through Kodi, but this will work for other integrations such as Plex, Emby, Apple TV, Roku, etc. My automation in Node-RED looks like this:
Click the image to get the JSON export for the flow
The flow is pretty simple: when Kodi is playing media, turn off the air purifier. Then, when Kodi is done playing media it will turn on the air purifier and set the mode to auto.
I may take this further and also adjust the thermostat to avoid turning on the furnace or air conditioner when something is playing. However, with a device like that it might be worthwhile to add a cooldown after the media player state has changed. Adjusting the thermostat, and by extension your central air, too many times in a short amount of time isn't the best for the health of your equipment.