Disabling or enabling the chat tone
The sound produced when the unit speaks is called a chat tone. It can be toggled from within the manage > feedback menu. Alternatively, you can use the commands volume mute tone and volume unmute tone to accomplish the same thing. To adjust the volume that chat tones and other system sounds are produced at, type volume set <level>, where <level> is a value between 0 and 100. More detail is available in the Companion manual.
Changing the chat tone
The chat tone is specified by the persona file your robot has active, and serves as a way to inform users of the unit's current persona. If no persona has been selected, then this is default. Each persona has three different chat tones included in it, one for a masculine voice, a neutral voice, and a feminine voice. Neutral voices sometimes sound like beeps instead of a vocalization.
To change the gender of your robot's voice, see manage > identity > gender > voice. Note that voice gender can be specified separately from physical and mental gender. (Physical and mental gender affect the pronouns that the unit will use to describe itself.) For more information, see the identity options chapter in the manual.
To change the sound of your robot's voice completely, you need to change the persona your robot is using. This can be as simple as selecting a new option from the persona menu, or a creation of your own. See the personas chapter in the Companion manual for more information on how to create personas.