Common VoIP Audio Issues and How to Fix Them
If you experience poor call quality, one-way audio, or no sound during VoIP calls, the steps below will help you resolve most issues.
1. Check Your Internet Connection
VoIP requires a stable internet connection.
Recommended minimum:
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Download: 5 Mbps or higher
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Upload: 5 Mbps or higher
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Low latency and minimal packet loss
Tips:
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Avoid using VoIP on public or unstable Wi-Fi networks.
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If possible, use a wired Ethernet connection instead of Wi-Fi.
2. Disable SIP ALG (Very Important)
SIP ALG (Session Initiation Protocol Application Layer Gateway) is a common cause of VoIP audio problems.
Common symptoms caused by SIP ALG:
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One-way audio
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No audio at all
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Calls dropping after a few seconds
What to do:
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Log into your router or firewall.
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Locate SIP ALG or VoIP ALG.
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Disable it completely.
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Save settings and reboot your router.
⚠️ If you are unsure how to do this, contact your network administrator or log a support ticket with CBNIT.
3. Check Firewall and Network Ports
Your firewall must allow VoIP traffic.
Ensure the following are not blocked:
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UDP ports 5060 – 5061 (SIP)
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UDP ports 10000 – 20000 (RTP audio)
If you are behind a corporate firewall, ask your IT provider to confirm these ports are open.
4. Verify Audio Codecs
Incorrect codec settings can cause poor or missing audio.
Recommended codec order:
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PCMA
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PCMU
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G729
Disable unused or unsupported codecs to improve call quality.
5. Check Device Volume and Audio Devices
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Ensure your headset or handset is correctly connected.
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Check that the correct microphone and speaker are selected in your softphone or device settings.
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Test audio using a different headset if possible.
6. Reboot Your Device and Router
A simple reboot can often resolve temporary VoIP issues:
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Restart your phone or softphone.
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Restart your router or modem.
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Try making a test call again.
One-Way Audio on VoIP Calls
One-way audio occurs when only one party can hear the other.
Most common causes:
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SIP ALG enabled
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Firewall blocking RTP ports
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NAT issues on the network
Recommended fix:
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Disable SIP ALG
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Ensure RTP ports are open
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Reboot the network after changes
