Native speech-to-speech models can make AI calls sound more natural, but in our experience they cost roughly twice as much per minute and are less predictable than the standard pipeline (speech recognition → language model → text-to-speech). For most high-volume Indian campaigns, a well-tuned pipeline is the right default. Speech-to-speech is worth testing for premium inbound experiences. Here's the trade-off, including what we saw when a hospital deployment ran on a native-audio model.
Compare both on your own script: Try Edesy free — Rs 50 free credit, no demo needed.
The two architectures
Pipeline: caller speaks → speech recognition (text) → language model (reply text) → text-to-speech (voice). Each part is swappable: you can pick the best Indian-language speech recognition, the model, and a voice that suits your brand.
Speech-to-speech: one native-audio model listens and replies in audio directly. Fewer hops, often smoother turn-taking and more expressive speech.
Compared
| Pipeline | Speech-to-speech | |
|---|---|---|
| Naturalness | Good, depends on voice choice | Often better |
| Interruption handling | Good with tuning | Often smoother |
| Cost per minute | Lower | Roughly 2x in our experience |
| Control over each part | High (choose STT, model, voice) | Lower |
| Indian-language coverage | Broad, voice by voice | Varies by model and language |
| Maturity / predictability | High | Improving |
On Edesy, native-audio (HD voice) agents are priced at a higher per-tier rate than standard agents; the exact rate shows in your dashboard.
What we saw in production
A multi-branch hospital ran patient follow-ups on a native-audio model. The calls sounded natural, but two issues showed up that you should test for:
- Silence in long calls: the agent went quiet after several minutes on some calls.
- Clipped first word: the start of some replies was cut off.
Neither is a reason to rule speech-to-speech out, but both are reasons to test long calls and your specific languages before a rollout, and to compare cost per outcome, not just how it sounds.
How to choose
- High-volume outbound campaigns (reminders, surveys, collections): pipeline. Cost and predictability win.
- Regional-language-heavy lists: pipeline, choosing the best voice per language.
- Premium inbound (a flagship receptionist, VIP lines): test speech-to-speech.
- Long calls (5+ minutes): test both carefully for silences and drift.
Test plan
- Build the same agent both ways.
- Run 30 calls each in your main language, including 5 long calls.
- Compare: outcome rate, interruptions handled, silences, cost per outcome.
- Listen to the first word of replies.
Latency matters for both; see low-latency Hinglish voice agents and how to fix dead air. For the model family behind many native-audio agents, see Gemini Live HD voice explained.
Cost
Standard agents on Edesy cost Rs 4-6 per started minute depending on your prepaid top-up; native-audio agents cost more. Unanswered calls are free either way.
Try both
Create a free account and run the test plan above on 60 calls. Want help choosing for a large rollout? Talk to us.