> ## Documentation Index
> Fetch the complete documentation index at: https://docs.getpatter.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Silero VAD
> ONNX-backed voice activity detection for fast, accurate barge-in in pipeline mode.
# Silero VAD
`SileroVAD` is Patter's bundled `VADProvider` — voice activity detection backed by the [Silero](https://github.com/snakers4/silero-vad) ONNX model. It buffers incoming PCM frames, runs inference on fixed-size windows (256 samples at 8 kHz, 512 at 16 kHz), applies an exponential probability filter, and emits `speech_start` / `speech_end` transitions.
Patter uses it to detect when the caller has started speaking so the agent can stop talking immediately (clean barge-in) and to gate STT activity on real speech instead of background noise.
## Install
Silero VAD ships as an optional extra (the ONNX runtime is \~210 MB):
```bash Python theme={null}
pip install "getpatter[silero]"
```
```bash TypeScript theme={null}
npm install getpatter onnxruntime-node@~1.18.0
```
The bundled `silero_vad.onnx` model file is included with the package.
## Auto-loading
When you build a pipeline-mode agent and leave `vad=None` (Python) / `vad: undefined` (TypeScript), Patter auto-loads `SileroVAD.for_phone_call()` / `SileroVAD.forPhoneCall()` for you on the first call.
If the optional extra is not installed, Patter logs a single warning and continues without VAD — barge-in latency is higher but the call still works.
To pick your own VAD or override the defaults, pass `vad=` explicitly. See the [`vad` parameter on Agents](/python-sdk/agents) (pipeline mode only).
## Constructor
The recommended entrypoint is the `for_phone_call` / `forPhoneCall` factory — it pins the sample rate to 16 kHz (what Patter's pipeline-mode audio bus uses) and applies the upstream Silero defaults.
```python Python theme={null}
import asyncio
from getpatter.providers.silero_vad import SileroVAD
# Recommended for telephony pipelines
vad = await asyncio.to_thread(SileroVAD.for_phone_call)
# Or, full control:
vad = SileroVAD.load(
activation_threshold=0.8, # Silero `threshold`; 0.8 tuned for telephony
deactivation_threshold=0.65, # `neg_threshold = threshold - 0.15`
min_speech_duration=0.25, # seconds, `min_speech_duration_ms = 250`
min_silence_duration=0.1, # seconds, `min_silence_duration_ms = 100`
prefix_padding_duration=0.03, # seconds, `speech_pad_ms = 30`
sample_rate=16000, # 8000 or 16000 only
force_cpu=True,
)
```
```typescript TypeScript theme={null}
import { SileroVAD } from "getpatter";
// Recommended for telephony pipelines
const vad = await SileroVAD.forPhoneCall();
// Or, full control:
const vad2 = await SileroVAD.load({
activationThreshold: 0.8,
deactivationThreshold: 0.65,
minSpeechDuration: 0.25,
minSilenceDuration: 0.1,
prefixPaddingDuration: 0.03,
sampleRate: 16000,
forceCpu: true,
});
```
### Phone-call preset (`for_phone_call` / `forPhoneCall`)
Identical to `load()` but pins `sample_rate` to 16000 Hz — the only sample rate Patter's pipeline-mode audio bus uses (8 kHz mulaw from Twilio is upsampled to 16 kHz PCM before reaching the VAD). Parameters are tuned for telephony-band audio (not the upstream Silero studio defaults):
* `activation_threshold = 0.8` — raised from upstream default 0.5 to filter background noise on telephony
* `deactivation_threshold = 0.65` — raised from upstream default 0.35 to match activation with no hysteresis gap
* `min_speech_duration = 0.25` — upstream `min_speech_duration_ms = 250`
* `min_silence_duration = 0.1` — upstream `min_silence_duration_ms = 100`
* `prefix_padding_duration = 0.03` — upstream `speech_pad_ms = 30`
Override any field via keyword arguments. Deployments that experience truncation on natural pauses can raise `min_silence_duration` (e.g. 0.5–1.0 s). To restore the upstream Silero defaults for studio audio, pass `activation_threshold=0.5, deactivation_threshold=0.35`:
```python Python theme={null}
vad = await asyncio.to_thread(
SileroVAD.for_phone_call,
min_silence_duration=0.5,
)
```
```typescript TypeScript theme={null}
const vad = await SileroVAD.forPhoneCall({ minSilenceDuration: 0.5 });
```
## Usage in a pipeline agent
```python Python theme={null}
import asyncio
from getpatter import Patter, Twilio, DeepgramSTT, AnthropicLLM, ElevenLabsTTS
from getpatter.providers.silero_vad import SileroVAD
phone = Patter(carrier=Twilio(), phone_number="+15550001234")
vad = await asyncio.to_thread(SileroVAD.for_phone_call)
agent = phone.agent(
stt=DeepgramSTT(),
llm=AnthropicLLM(),
tts=ElevenLabsTTS(voice_id="rachel"),
vad=vad, # explicit, or omit to auto-load
system_prompt="You are a helpful assistant.",
)
await phone.serve(agent)
```
```typescript TypeScript theme={null}
import { Patter, Twilio, DeepgramSTT, AnthropicLLM, ElevenLabsTTS, SileroVAD } from "getpatter";
const phone = new Patter({ carrier: new Twilio(), phoneNumber: "+15550001234" });
const vad = await SileroVAD.forPhoneCall();
const agent = phone.agent({
stt: new DeepgramSTT(),
llm: new AnthropicLLM(),
tts: new ElevenLabsTTS({ voiceId: "rachel" }),
vad, // explicit, or omit to auto-load
systemPrompt: "You are a helpful assistant.",
});
await phone.serve({ agent });
```
## When to use Silero VAD vs alternatives
* **Use Silero VAD** for any pipeline-mode agent that needs sub-300 ms barge-in. It's the production default.
* **Skip VAD** (pass `vad=None` and don't install the extra) only when you're prototyping locally on a system where the ONNX runtime is awkward to install. Barge-in falls back to a sustained-voice heuristic that is slower and noisier.
* **Realtime engines** (`OpenAIRealtime`, `GeminiLive`, `UltravoxRealtime`) run server-side VAD inside the provider — `agent.vad` is ignored in engine mode.
## Notes
* The model only supports 8000 or 16000 Hz inference. Other sample rates raise on `process_frame` / `processFrame`.
* Inference runs in a thread executor (Python) or asynchronously (TS) so the event loop stays responsive. Patter logs a warning if a single window takes more than 200 ms.
* The TS resolver probes multiple paths to find `silero_vad.onnx`, including under bundlers (Vite SSR, Next webpack, Bun). If you see `model file not found`, install with `npm install onnxruntime-node@~1.18.0` and ensure `getpatter` is fully installed in your `node_modules`.
## What's Next
The `vad` parameter on `phone.agent(...)`.
Proprietary noise / echo suppression.
OSS noise suppression.
STT + LLM + TTS composition.