Sending real-time audio over a data network is demanding on every component in the chain, and the performance required of your computer and network interact in complicated ways. For example, if you're communicating exclusively with other people over a high-speed local network and you aren't worried about eavesdropping, you don't need to enable either compression or encryption, both of which require a great deal of computation. For such an application a 386 machine is perfectly adequate. If your network link is slower, you'll have to compress the sound before it's transmitted. The most effective form of compression provided by Speak Freely, that used by GSM digital cellular telephones, reduces the data bandwidth requirement by almost a factor of five but is so computationally intense it can be done in real time only on a fast 486 or Pentium machine. Encryption also takes time; the three methods available vary in the computation required. Compression reduces encryption overhead since there's less to encrypt.
Whether Speak Freely will work effectively for you depends upon your CPU speed, network bandwidth, load on the network, and the compression and encryption modes you select in a complicated and subtle manner. The best way to find out is to try it; if it works, great; if it doesn't, try again when you next upgrade your computer or network connection. Speak Freely provides a built-in performance benchmark to assist you in selecting modes appropriate for your computer. You can experiment to determine which settings work best by connecting to an echo server which returns any sound you send to it after a 10 second delay.