1️⃣ Fix OS-level microphone gain (MOST IMPORTANT)

🔹 Windows (very common in call centers)

1. Control Panel → Sound → Recording

2. Select USB Headset Microphone

3. Click Properties

4. Go to Levels

   • Set Microphone → 90–100

   • Set Microphone Boost → +10 dB or +20 dB

5. Apply & OK

✅ Speak and confirm the green bar reaches 70–80%

🔹 macOS

1. System Settings → Sound → Input

2. Select USB Headset

3. Increase Input Volume to max

4. Disable Use ambient noise reduction (if shown)

2️⃣ Fix USB headset driver issues (CRITICAL)

🔹 Windows – reinstall USB audio driver

1. Press Win + X → Device Manager

2. Expand Sound, video and game controllers

3. Right-click USB Audio Device / Headset

4. Click Uninstall device

5. ✔ Check Delete driver software

6. Reboot

7. Plug headset back in → Windows reinstalls driver

👉 This fixes stuck low gain issues.

3️⃣ Disable “exclusive mode” (often overlooked)

Windows

1. Recording → Mic → Properties

2. Advanced tab

3. Uncheck:

   • ❌ Allow applications to take exclusive control

   • ❌ Give exclusive mode applications priority

4. Apply

This prevents softphone from locking mic at low gain.

4️⃣ Fix softphone microphone handling (VERY important)

Common settings (Zoiper / Linphone / MicroSIP)

Inside softphone Audio settings:

✔ Select USB Headset mic explicitly
❌ Do NOT use “Default”
✔ Enable Automatic Gain Control (AGC)
❌ Disable Noise Suppression (test)
❌ Disable Silence Suppression / VAD

Then restart softphone.

5️⃣ Hardware-level checks (quick but important)

Ask her:

• Is headset USB or 3.5mm?

• Does headset have inline volume wheel?

• Any mute button partially pressed?

Very often the inline wheel is set low.