How can I force the rediscovery of PulseAudio virtual sound devices?

Solution 1:

1. On the "Sink" PC (On whose speaker you wanna play the sound) open the PulseAudio command shell by going into Terminal and issuing the following command.
   
   $ pacmd
   
   You will see a Python-like shell with the following welcome message.
   
   Welcome to PulseAudio! Use "help" for usage information. >>>
2. List the devices that can play the sound on the PC by the command in the PulseAudio shell.
   >>> list-sinks
   Now you'll see a detailed list of all the sound sinks.
3. Just note down the complete name of the sink of your choice. It would appear as an attribute of the sound card. For example in my case it is:
   
   1 sink(s) available. index: 0 name: <alsa_output.pci-0000_00_1b.0.analog-stereo>
   ...

The string of my interest is just "alsa_output.pci-0000_00_1b.0.analog-stereo"

4. Now Go onto the Source PC (i.e. origin of the audio multimedia streams), open up the terminal and issue the following command
   
   $ pactl load-module module-tunnel-sink "server=192.168.1.105 sink=alsa_output.pci-0000_00_1b.0.analog-stereo sink_name=home_theater"
   
   Here 192.168.1.105 is the IP address of the sink PC, "alsa_output.pci-0000_00_1b.0.analog-stereo" is the string you just copied from sink's terminal and "home_theater" is just a fancy name to call this virtual sound output device on your computer.
   
   
5. Finally select this virtual sound device by :
   $ pacmd set-default-sink home_theater
   
   Wallah !!

Solution 2:

A simple sudo service avahi-daemon restart does the trick, even though avahi-browse sees the devices before that avahi restart. Thanks to Takkat for pointing me in the right direction.