audio settings when connecte to hdmi external monitor

@db-eco  if your earbuds are a headset, i.e. built-in mic, rather than basic headphones, then forget about using the audio output built into the display.  That would only be designed for attaching headphones or speakers.  It likely doesn't even have wiring for receiving a mic signal, because although HDMI technically does support an audio return channel, I've never seen it implemented for this type of use case of enabling headsets to be plugged into displays and pass audio back down to a PC.  The only time I've seen HDMI ARC (Audio Return Channel) implemented is on AV receivers and TVs, since that capability means your TV can send audio from its built-in apps down to the receiver for output through your surround sound system, using the HDMI cable that's also often carrying video from the receiver up to the TV.  Without HDMI ARC, you'd need to also connect a separate audio cable from the TV back down to the receiver for that scenario.  But I've never seen a PC support receiving audio on its HDMI port, which come to think of it might be because I don't know if HDMI supports carrying audio in both directions simultaneously.

However, this is still completely fixable, and you're in the right place under Control Panel > Sound.  What you want to do is set your default audio device and default communications device to your Realtek Speakres/Headphones device, even while the display is plugged in.  That way audio will continue to play out of either the laptop's built-in speakers or a headset that you plugged into its jack.  In terms of the mic, switch from the Playback tab over to the Recording tab in Control Panel > Sound and make sure that the Realtek device over there is set as the default recording device, in which case the system will use either the built-in mic or a headset mic if you have one plugged in.

Alternatively, if you normally WANT to have most of your system audio going to the display because you have speakers attached there and only want to have Zoom use different playback and mic devices, then Zoom itself allows you to tell it to use non-default playback and recording devices just for its audio, as do most other popular conferencing apps.  As a result, you don't necessarily have to change the Windows default devices to achieve the desired behavior within Zoom and other such apps, although you might still find it convenient to do so.

@db-eco  in addition to my reply above, I didn't specifically call this out, but fyi you can also mix and match your audio playback and recording pairings at will.  So for example, you could set your playback device to be the HDMI-attached display in order to have audio go to external speakers attached to that display, while continuing to use your Realtek device as the recording device in order to use either the laptop's built-in mic or a headset plugged into the laptop's headset jack.  You can achieve this either by setting the default playback and recording devices as desired or by customizing settings within Zoom.  However, be aware that if you use external speakers for playback and the laptop's built-in mic for input, you might end up generating audio feedback for everyone else on the call as the mic might pick up the audio generated by the external speakers.  If you're wondering how this problem is avoided in setups like conference room tabletop speakerphones or full TelePresence-type setups, it's because those devices and setups have algorithms cause their mics to cancel out the audio that they're playing through their own speakers -- but that type of cancellation only works when the same device is handling both audio output and input.  It doesn't work when you're splitting those roles between completely separate devices that aren't coordinating with each other.  Some built-in mics and headset mics have general ambient noise cancellation mechanisms or are tuned to pick up only audio within a narrow "listening cone", but that varies from device to device and isn't as intelligent as cancelling out the specific audio that is playing from the conference.

@db-eco  sorry for the triple post here, but if you want to know where to adjust the audio output and mic device selections within Zoom, in a meeting you should have a Mute/Unmute toggle button in the lower-left corner of the meeting window.  Directly to the right of that you'll see a carat icon (^).  Click that and you'll see a menu allowing you to choose your output and mic devices, which will be specific to Zoom, meaning you don't have to change your entire Windows settings if you don't want to.

Hi again jphugan. Apologies for the delayed response. I didn't have a chance to work on this until two days ago and then this forum was not letting me log back in, even though it said I was already logged in.

I found the audio settings for Zoom. They were a bit buried. But when I attached the new Logitech headset I purchased over the weekend (I'm going to need it because I'm teaching at one college and am a program chair at another), I was able to change the settings to what I needed. (That setting wasn't available when I had just the cheapo headset - with mic - that came with my cellphone.) Interestingly, one other app similar to Zoom then automatically recognized the settings. I haven't tried Google Hangouts yet, which had been giving me even more problems, but I have a suspicion it will be now be fine, too. If not, I'll dig further to find its audio settings.

Thanks again.