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.
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.
Configuration via API
PATCH /v2/ip_connections/ with the noise_suppression object:
{
"noise_suppression": {
"direction": "both",
"noise_suppression_engine": "Denoiser"
}
}
noise_suppression object:
{
"noise_suppression": {
"direction": "inbound",
"noise_suppression_engine": "Krisp Viva Tel Lite"
}
}
Supported engines
Use the noise_suppression_engine parameter to select an engine. If omitted, Denoiser is used.
| Engine | Value | Description | Best for |
|---|
| Denoiser | Denoiser | Built-in, general-purpose noise reduction | Default option for most calls |
| DeepFilterNet | DeepFilterNet | Open-source, full-band 48 kHz processing | Telephony and WebRTC |
| Krisp Viva Tel Lite | Krisp Viva Tel Lite | Telephony up to 16 kHz, isolates primary speaker | Telephony with speaker isolation |
| Krisp Viva Pro | Krisp Viva Pro | WebRTC 16–32 kHz, full voice isolation | Close-microphone WebRTC calls |
| Krisp Viva SS | Krisp Viva SS | WebRTC 16–32 kHz, far-field optimized | Smart speakers and far-field microphones |
| AI-coustics Quail | AI-coustics Quail | STT-optimized, up to 43% WER reduction | AI and speech recognition workloads |
Krisp Viva Tel Lite when you need to isolate the primary speaker from background voices.
Direction options
The direction parameter controls which audio streams are processed:
| Value | Description | Use case |
|---|
inbound | Processes audio from the PSTN to your system | Clean up audio received by your users or applications |
outbound | Processes audio from your system to the PSTN | Reduce background noise from your users or applications |
both | Processes audio in both directions | Maximum call clarity when both sides may have background noise |
disabled | Turns off noise suppression | Preserve natural ambient sounds when needed |
Codec compatibility
Noise suppression works with standard SIP trunking codecs including:
- G.711 (μ-law and A-law)
- G.722
- Opus
- 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
Best practices
- Use connection-level configuration for consistent audio quality across all phone numbers
- Enable bidirectional suppression (
both) for optimal results in noisy environments
- Test with your specific use case to balance noise reduction with audio naturalness
- Monitor call quality metrics to validate the impact on your application
