Hi there! I understand you're hearing a big echo when using the DoubleDown News app on your iMac, and it's bothering you enough to switch off the video. Let's work together to sort this out so you can enjoy the app without that echo.

To help me better assist, could you tell me a bit more? Does the echo happen only when the video is on, or does it persist even with just audio? Also, are you using any external speakers or headphones, or just the iMac’s built-in sound?

In the meantime, here are some steps you can try to reduce or eliminate the echo on your iMac (macOS 10.15.7):

1. Check Sound Output Settings:
- Click on the Apple menu > System Preferences > Sound.
- Under the 'Output' tab, make sure the correct device is selected (e.g., Internal Speakers if not using headphones).
- Lower the output volume a bit to see if that reduces echo.

2. Mute Other Audio Sources:
- Ensure no other apps or browser tabs are playing audio simultaneously, as multiple audio streams can cause echoes.

3. Close and Restart the DoubleDown News App:
- Sometimes, restarting the app can reset audio channels.

4. Disable System Audio Effects:
- Go to System Preferences > Sound > Sound Effects.
- Turn off effects like “Play feedback when volume is changed,” which might interfere.

5. Check for Multiple Audio Devices:
- If you have Bluetooth speakers or headphones connected, try disconnecting them temporarily to see if the echo stops.

6. Update the DoubleDown News App:
- Check if there is an update available for the app in the Mac App Store. Sometimes bug fixes address audio issues.

7. Restart Your iMac:
- A simple restart can fix many audio glitches.

If after trying these, the echo persists only while video is on, it's possible the app or its video player is causing an audio loop or syncing issue. In that case, could you let me know if this happens with other videos or apps?

I’m here to help you get through this! Let me know what you find after these steps or any details about how you're using the app.