System 7.5.5: Muted Sound With FreePPP (5/97)

I recently installed some Internet software on a Power Macintosh 7300 and on a Power Macintosh 9600. Both systems are running System 7.5.5. After installation, the alert sound is muted. Instead of a beep sound, the menubar flashes when the system issues an alert. I have tried unsuccessfully to restore the system alert sound. How can I resolve this issue?
With System 7.5.5, having the FreePPP extension in the System Folder disables sound on some Power Macintosh systems. There are two solutions:

Open Transport PPP can be found in the Apple Extras folder on Power Macintosh 7300, 8600, and 9600 systems.
Published Date: Feb 18, 2012