"One-way audio" is a common communication glitch where audio only travels in one direction. Depending on whether you are using an ONSIM SIM in a mobile device or a VoIP Desk Phone/Handset, the cause and the fix are very different.
📱 For ONSIM SIM Users (Mobile)
If you are using an ONSIM SIM and experience silent gaps or one-way audio, the issue is usually related to how your phone "talks" to the local cell tower.
1. Toggle VoLTE (4G Calling)
VoLTE allows your voice to travel over the 4G data network. Sometimes, if the local mast is congested or the "handshake" fails, the audio stream can drop in one direction.
The Fix: Go to your phone's Cellular/Mobile Data Settings and toggle VoLTE (or "4G Calling") OFF, wait 10 seconds, then toggle it back ON. This forces a fresh connection to the voice gateway.
2. Test via Wi-Fi Calling
To determine if the problem is with the physical cell tower in your area or the phone itself:
The Fix: Enable Wi-Fi Calling in your phone settings and connect to a stable Wi-Fi network. If the audio works perfectly on Wi-Fi but fails on 4G, the local mobile mast is likely experiencing a "timing" issue with its data packets.
☎️ For VoIP Handset Users (Desk Phones)
If you are using a physical VoIP phone (like a Yealink or Polycom) behind an office or home router, the issue is almost always a "firewall" setting.
1. Disable "SIP ALG" (The #1 Culprit)
Most modern routers have a feature called SIP ALG (Application Layer Gateway) enabled by default. While it sounds helpful, it actually "inspects" and often corrupts VoIP data packets, leading to one-way audio or dropped calls.
The Fix: Log in to your router's admin panel, search for "SIP ALG" (usually under Firewall or Advanced Security settings), and set it to Disabled.
2. Check NAT/Firewall Ports
If your router’s firewall is too restrictive, it may allow the "Outbound" audio out but block the "Inbound" audio from reaching your desk phone.
The Fix: Ensure your network allows traffic on the standard VoIP ports (typically SIP 5060 and RTP 10000-20000).
📋 Quick Diagnostic Summary
| Symptom | Likely Cause | Primary Fix |
|---|---|---|
| Mobile: Silence on one end | Mast Handover/VoLTE | Toggle VoLTE Off/On |
| Mobile: Works on Wi-Fi only | Local Signal Issue | Report to ONSIM Support |
| Desk Phone: Immediate 1-way audio | Router Interference | Disable SIP ALG in Router |
| Desk Phone: Random 1-way audio | Network Congestion | Enable Quality of Service (QoS) |
🛠️ Still Experiencing Issues?
If these steps haven't resolved the problem, please raise a ticket with our support team. To investigate "One-Way Audio," our engineers need to trace the call data, so we will need specific examples (time, date, and numbers involved).
The fastest way to get help is to raise a support ticket directly through your ONSIM Dashboard.
Click here for our guide on creating a support ticket via the online portal.