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Voices

Every Nixflex agent speaks with a voice. You can set it at two levels: a default voice on the agent, and an optional per-number voice that overrides it for a specific phone number.

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Two ways to set a voice

Agent default — the voice used by every number on the agent unless a number overrides it. Set the voice_id field on the agent:
Per-number override — give one phone number its own voice, regardless of the agent default. This is essential when one agent serves many numbers (for example a reseller running 200 clinics on a single agent) and each number needs to sound different. Set voice_id on the number:
A number with its own voice_id uses that voice; a number without one falls back to the agent’s voice. Changes take effect on the next call — no redeploy. See Update phone number for the full endpoint. Per-number voice applies to both inbound and outbound calls. The voice is resolved from the number the call uses: the dialled number for inbound, the from_number for outbound, so a number sounds the same in both directions. Set it once; if it ever gets cleared, set it again before the next call.
voice_id must be an exact, valid voice ID (for example Olivia, Craig, Ashley). An unrecognised value falls back to the agent’s voice rather than erroring, so if a voice isn’t changing, check the value is exact.
These voices work well for phone receptionists and business calls — warm, clear, and professional.

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Multilingual voices

Some voices speak several languages while keeping the same identity. For example, Olivia can speak English, German, Spanish, and Arabic. Set the language field to choose which language the voice speaks on a call.

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Speaking speed

How fast the agent talks. 1.0 is normal, 0.5 is half speed, and 1.5 is half again as fast. A value outside that range is clamped to the nearest limit rather than rejected. Like the voice, speed can be set at two levels. Agent default — set it in the dashboard, or send speaking_rate when you create or update the agent. Every number on that agent speaks at this speed unless the number overrides it.
speaking_rate is the field that controls speed. The older voice_speed field on the agent is still accepted and returned for backwards compatibility, but nothing reads it - setting it has no effect. See Create agent.
Per-number override — set speaking_rate on the number:
A number with its own speed uses it. A number without one falls back to the agent. An agent without one speaks at normal speed. So if you set the agent to 1.5, every number on that agent speaks at 1.5 - including numbers you have never touched. Only a number with its own speaking_rate is exempt.
null and 1 are not the same thing.
  • null means not set. The number inherits the agent’s speed, so a number set to null under a 1.5 agent still speaks at 1.5.
  • 1 means explicitly normal. It overrides the agent, so a number set to 1 under a 1.5 agent speaks at normal speed.
To bring one number back to normal while the rest of the agent stays fast, send 1 - not null.
Speed applies to both inbound and outbound calls and takes effect on the next call, like the voice itself.
Small steps go a long way on a phone line. 0.9 already sounds noticeably more measured and 1.1 noticeably brisker, so adjust a step at a time rather than jumping to the limits.

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Preview before you go live

Always listen to a voice before using it on real calls. A dental clinic wants a calm, professional voice; a sales line might want something more energetic.