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Documentation Index

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Noise suppression enhances call quality by removing background noise from audio streams. Configure this feature at the connection level or individual phone number level to reduce unwanted ambient sounds during calls.

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Configuration scope

Noise suppression can be configured at two levels:
  • Connection level: Applied to all phone numbers associated with the SIP connection. This setting overrides individual number configurations.
  • Number level: Applied to specific phone numbers for granular control.
Connection-level settings take precedence over number-level configurations, simplifying management and ensuring consistent audio quality across all calls.

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Configuration via API

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Configure at connection level

PATCH /v2/ip_connections/ with the noise_suppression object: 
{
  "noise_suppression": {
    "direction": "both",
    "noise_suppression_engine": "Denoiser"
  }
}

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Configure at number level

PATCH /v2/phone_numbers//voice with the noise_suppression object: 
{
  "noise_suppression": {
    "direction": "inbound",
    "noise_suppression_engine": "Krisp Viva Tel Lite"
  }
}

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Supported engines

Use the noise_suppression_engine parameter to select an engine. If omitted, Denoiser is used.
EngineValueDescriptionBest for
DenoiserDenoiserBuilt-in, general-purpose noise reductionDefault option for most calls
DeepFilterNetDeepFilterNetOpen-source, full-band 48 kHz processingTelephony and WebRTC
Krisp Viva Tel LiteKrisp Viva Tel LiteTelephony up to 16 kHz, isolates primary speakerTelephony with speaker isolation
Krisp Viva ProKrisp Viva ProWebRTC 16–32 kHz, full voice isolationClose-microphone WebRTC calls
Krisp Viva SSKrisp Viva SSWebRTC 16–32 kHz, far-field optimizedSmart speakers and far-field microphones
AI-coustics QuailAI-coustics QuailSTT-optimized, up to 43% WER reductionAI and speech recognition workloads
For SIP trunking, Denoiser and Krisp Viva Tel Lite are the most common choices. Use Krisp Viva Tel Lite when you need to isolate the primary speaker from background voices.

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Direction options

The direction parameter controls which audio streams are processed:
ValueDescriptionUse case
inboundProcesses audio from the PSTN to your systemClean up audio received by your users or applications
outboundProcesses audio from your system to the PSTNReduce background noise from your users or applications
bothProcesses audio in both directionsMaximum call clarity when both sides may have background noise
disabledTurns off noise suppressionPreserve natural ambient sounds when needed

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Codec compatibility

Noise suppression works with standard SIP trunking codecs including:
  • G.711 (μ-law and A-law)
  • G.722
  • Opus

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Performance considerations

  • Each direction (inbound/outbound) is processed and billed independently
  • Processing adds minimal latency (typically < 20ms)
  • Noise suppression is applied in real-time during the call
  • Connection-level configuration provides consistent behavior across all numbers

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Best practices

  1. Use connection-level configuration for consistent audio quality across all phone numbers
  2. Enable bidirectional suppression (both) for optimal results in noisy environments
  3. Test with your specific use case to balance noise reduction with audio naturalness
  4. Monitor call quality metrics to validate the impact on your application