Hitting things together can provide some kind of sound signal. Rock on rock, wood on wood, metal on metal. Hitting something hollow better than something solid, but "needs must."

Blast might coach us on a series of small explosions or fast exothermic reactions from household products you probably [could] have in your gear.

Perhaps a percusionist among us could provide ideas on improvising drums? bells? chimes?

Perhaps a vocalist among us could give tips on yodeling or other use long distance voice signals?

Really. really awful puns might inspire your companions to provide copious low frequency groans?