West Africa brought their goods to the trading center, beat the drum, and left
North Africans come in and check to see if they liked the amount, if they did, they leave their gift, if they don't; they would beat on the drum and leave without leaving a gift.
West Africans come back to the trading center, realize they need to leave more gold, go back to West Africa and deliver more gold to the trading center and drop it off. They leave after beating the drum.
Some advantages of silent barter trading
West Africans leave the site and North Africans come and judge if there is enough gold. If there is, they leave the salt, beat on the drum, and leave.
West Africans come, take the salt that was left for them, and leave.
Some of the good thing that could come from silent trading were They could avoid language barriers and Avoid conflict with others trading.