Voice Boxes are Synth modules that allow Synths to vocalize. The generate noises and allow Synths to have an audible voice, giving them the ability of speech. The two main types of voice boxes used are vocal cord based and chip based voice boxes. Voice boxes are installed within the Synth's throat, in the same position the larynx would be found in with organics, regardless of type.
Vocal cord based voice boxes contain synthetic vocal cords, that are almost identical to those found in humanoid organics. Consisting of elastic polymers, they vibrate in the inhaled or exhaled air, generating a voice in the process. The Synth can modulate their voice through the movement of their vocal cords just as organics do. Vocal cord based voice boxes will typically change their size depending on the blueprint used by the Synth and can grow or shrink along with the Synth's body. This also changes the pitch of the Synth's voice.
Chip Based voice boxes emulate the function of vocal cord based voice boxes with the use of a speaker instead of physical vocal cords. The voice modulation, pitch and timber are calculated by a sound processor included in the voice box. Chip based voice boxes don't automatically change their pitch based on the Synth's size, so if the Synth wishes their voice to change with their size, their sound parameters need to be adjusted manually from time to time.
Even though Synths are very modular and almost every part can be exchanged with new ones, voice boxes are only rarely exchanged. This is due to each Synth having a unique voice. Exchanging voices is seen as a very drastic step, since it usually means a change to the voice both the Synth and their peers are used to hearing. Chip based voice boxes are easier to exchange, since sound settings can simply be copied over to a new voice box. With vocal cord based voice boxes, exchanges typically happen, when a Synth is unsatisfied with their voice, or wants their voice to fit more with their desired gender expression.
Synth Voices sound very similar to organic voices, but often have a computer-like trill to them, giving them a subtle, but noticable difference in their voices.