VAD and Interruptions

Voice Activity Detection (VAD) identifies when speech is present in an audio stream. It acts as a first-pass filter and enables interruption handling in your pipeline by signaling when a user starts talking. Zero Runtime uses Silero VAD for speech-activity detection; for the most reliable results, pair VAD with a turn detector.

Configure Silero VAD

Configure VAD and pass it to your Pipeline as the vad component:

from zrt.plugins import SileroVAD

# Configure VAD to detect speech activity
vad = SileroVAD(
    threshold=0.5,                # Sensitivity to speech (0.3 to 0.8)
    min_speech_duration=0.1,      # Ignore very brief sounds
    min_silence_duration=0.75     # Wait time before considering speech ended
)

Interruption Detection

Interruption Detection decides when user speech should stop the agent mid-response. It can use VAD, STT, or both. This avoids false triggers from short noises, filler words, or background audio. Using VAD detects raw speech activity. It is faster but can be triggered by background noise.

from zrt import Pipeline, InterruptConfig

pipeline = Pipeline(
    # ... other config
    interrupt_config=InterruptConfig(
        mode="VAD_ONLY",
        interrupt_min_duration=0.2  # 200ms of continuous speech
    )
)

Using STT relies only on recognized words from the transcript. It is slower but ensures the speech is intelligible.

from zrt import Pipeline, InterruptConfig

pipeline = Pipeline(
    # ... other config
    interrupt_config=InterruptConfig(
        mode="STT_ONLY",
        interrupt_min_words=2  # At least 2 words recognized
    )
)

Use HYBRID mode to require both audio detection and recognized words.

False Interruption Recovery

A false interruption is a brief accidental noise, like a cough, an “mm-hmm”, or background noise, that should not stop the agent. Instead of cutting off immediately, InterruptConfig lets the agent pause and confirm whether an interruption is genuine before deciding to stop or resume speaking.

How it works

Maybe-interruption

The user makes a sound while the agent is speaking. Instead of cutting off, the agent pauses TTS and starts a timer (false_interrupt_pause_duration).

Confirm or resume

If a transcript with at least interrupt_min_words words arrives before the timer expires (or VAD confirms sustained speech), it’s a real interruption and the agent stops. Otherwise the timer expires and the agent resumes speaking from where it paused.

Enable it

Set resume_on_false_interrupt=True on the pipeline’s InterruptConfig. Tune false_interrupt_pause_duration for how long to wait before deciding it was a false alarm.

from zrt import Pipeline, InterruptConfig

pipeline = Pipeline(
    # ... other config
    interrupt_config=InterruptConfig(
        false_interrupt_pause_duration=2.0,  # Wait 2 seconds to confirm
        resume_on_false_interrupt=True       # Auto-resume if interruption is brief
    )
)

Configuration

Parameter	Type	Default	Description
`mode`	`"VAD_ONLY"` \| `"STT_ONLY"` \| `"HYBRID"`	`"HYBRID"`	Detection method for interruptions.
`interrupt_min_duration`	`float`	`0.5`	Minimum speech duration in seconds to trigger an interrupt.
`interrupt_min_words`	`int`	`2`	Minimum words needed to confirm an interrupt.
`false_interrupt_pause_duration`	`float`	`2.0`	Pause duration in seconds on a false interrupt, before deciding it was false and resuming.
`resume_on_false_interrupt`	`bool`	`True`	Whether to resume agent speech after a false interrupt.

What’s Next

Turn Detection

Pair VAD with semantic turn detection.

De-noise

Give VAD a cleaner audio signal.

References

Python

Examples

Cascade Basic

Voice agent with VAD configured.

SDK Reference

VAD

VAD in the Python API reference.

Utterance Handle

Utterance Handle in the Python API reference.

Get started

Modalities

Configure Pipeline

Tools and Capabilities

Turn Detection and Interruptions

Telephony Agents

Context Management

Observability and Monitoring

Configure Silero VAD

Interruption Detection

False Interruption Recovery

How it works

Enable it

Configuration

What’s Next

Turn Detection

De-noise

References

Examples

Cascade Basic

SDK Reference

VAD

Utterance Handle

​Configure Silero VAD

​Interruption Detection

​False Interruption Recovery

​How it works

​Enable it

​Configuration

​What’s Next

Turn Detection

De-noise

​References

​Examples

Cascade Basic

​SDK Reference

VAD

Utterance Handle

Configure Silero VAD

Interruption Detection

False Interruption Recovery

How it works

Enable it

Configuration

What’s Next

References

Examples

SDK Reference