The gig of these times -- you hope no one shows up! I like to wear earplugs in these situations. It makes everything softer, including the band, but I find that I can zone in on the music more if the sound is not overwhelming and have a shot at enjoying myself. Playing louder just feeds a vicious cycle. The band needs to play softly for themselves. Think of the old days when the unamplified bassist had to really dig into the sound to hear themselves. FWIW these are the earplugs I have. They're cheap and seem to attenuate frequencies fairly evenly and accurately.
Etymotic Research ETY-Plugs High Fidelity Earplugs - Standard Fit | Sweetwater Invalid Link Removed
Etymotic Research ETY-Plugs High Fidelity Earplugs - Standard Fit | Sweetwater Invalid Link Removed