The symbiote voice is the voice that Goa'uld and Tok'ra symbiotes are capable of making while in Human hosts. The voice is deep and echoing, and frightening to many who haven't heard it before. Anubis also used it to speak with people on the lower planes even after his ascension. However, it is not necessary for the symbiote to use it while speaking, and since the fall of the System Lords, many Goa'uld have taken to talking in a normal voice. The voice may simply be used as a method of intimidation that the Goa'uld use, or as a means to separate themselves from humans and make it easier to pose as gods. (Stargate) (SG1: "Children of the Gods", "Revelations", "Reckoning, Part 1", "Reckoning, Part 2", "Threads", "Beachhead")

The Tok'ra also use the symbiote voice, but their use of it seems to be a method of differentiation between host and symbiote. Since the Tok'ra work with their hosts and each individual retains their own mind, they generally use the voice to indicate that the symbiote is speaking, while using the host's natural voice means that they are the one speaking. There is usually a pause between the two while the individual who wishes to communicate takes control of their shared body. (SG1: "The Tok'ra, Part 1", "The Tok'ra, Part 2")

The SGC had a device that could reproduce the symbiote voice. (SG1: "Proving Ground")

Vala Mal Doran had a necklace device that could simulate the symbiote voice, allowing her to impersonate the Goa'uld Qetesh, who previously used her as a host. (SG1: "The Powers That Be")