I recorded myself yelling "no" and i used audacity to lower the pitch and i made it louder and added an echo then i recorded myself making a weird sound and lowered the pitch and echoed and made it louder and put then together why was this so hard to freaking type.
Dropped a plastic bottle over some plastic sandals, recorded this with a phone and wo mic to record directly to my computer inside audacity and edited noise out. Use it freely no need to attribute anything.