The 'bloop' is a beep for the other person being dumped onto the call. Typically in a call center/contact center system like this, the agent's headset is always live. When the 'bloop' comes in, it's an audible cue for the agent to actually pick up themselves as their ringtone on the line. At the end of the call they hit 'release' and wait for the next 'bloop' to go live again.