Shut off cable box, press menu button until white screen comes up. Change the HDMI settings to L-PCM, close out menu, turn on cable box back on. This should work, hopefully.. So far it's working as of this post.
Reading different blogs about the audio problem going from HD to non-HD, it appears to be a “handshake” issue between the "larger" Comcast Motorola Box and the television. We have an Insignia that is about 5 years old and also have just recently purchased a new LG (within the last 30 days). There has never been a problem with the LG (plug and play); however the Insignia has not been so lucky.
What has worked for us is the following prescription:
Turn TV on along with the larger Comcast Box (as the smaller Comcast Box appears to have no “plug and play” issues with older sets) and tune it to a non-HD channel
Turn Comcast Box off (at front button) and leave TV on
Push Menu button on remote (and possibly again) until white Menu dialog box appears
Scroll down to “Advanced HDMI Setting” and select
Scroll down to “Audio Output” and change “Auto” to “L-PCM” (as our Insignia TV setup, under audio S/PDIF has two audio selections “RAW and PCM” – however this selection on the TV does not affect the Comcast box setting)
Select “Menu” on remote, to close dialog out (leave TV on)
Turn Comcast Box back on, as audio for non-HD channels should now work.
It might be the TV not handling the box switching resolution well. You could try changing the box's settings so it does not switch its output resolution when you change channels.
Most older boxes have a setting to choose the output resolution (480i, 480p, 720p or 1080i) and the box will scale all output to that resolution. However, there is also an override setting so the box can force the output resolution of 4:3 SD channels to 480i or 480p. This is preferred if your TV has better scaler than the box and also allows the zoom/stretch to be changed on the TV. I think this is turned on by default and might have something to do with your problem.
When the output resolution changes there might be HDMI handshaking issues between the TV and box. If the box is connected with HDMI, it might be fine with component cables. I've never had this problem so I don't know. You should try making sure this 4:3 override is set to stretch (fills screen) or off (adds bars to side). Then the box will do the scaling itself and keep it's output resolution the same.
To turn off the 4:3 override, turn the box off and press Menu on the Comcast remote. Leave the TV on so you can see this menu. If the 4:3 override is set to 480i or 480p, hit down a couple times to select that and then right until stretch or off is selected, based on your preference. Hit menu again to exit then you can turn the box back on.
Though on some newer boxes the menu is slightly different... they allow you to choose the resolutions supported by your TV and then will change its output based on the channel's broadcast resolution. If this is the case then you could try enabling only one resolution (720p or 1080i).
i read around on the web and found out that some people had a language button on their remote and when they changed it from SAP to Stero they got their sound back. Someone else said they needed to change an audio setting from SAP to English or something like that. I do not have a Language button on my remote so what I tried was. Spoiler alert: I thought it worked at first but I was wrong!
1. using your remote touch the menu button
2. select settings
3. select audio setup
4. change the audio output to stereo. (mine was on "tv speakers")
i thought this worked at first but it didnt work when I changed channels again because I am pretty sure the loss of sound has something to do with going from a non hd channel to and hd channel.
so, after experimenting by changing channels each time I turned the tv on so that it had sound when I started here is what happened:
on a non hd channel upon turn on non hd to hd=sound ok
on and hd channell upon tunr on the tv had a blue box that said "lost HDCP connection" and then that goes away and there is sound and when you turn from the hd channel to non hd=no sound
I have the same volume problem I have to turn the tv off to get volume and cannot go back and forth between channels during commercial breaks because I lose sound. I miss the outcome of shows. What am I paying for? When you call they always act like they will try to fix your problem by trying some things when it seems like problems should be standard and they should say "I know what that is and here is the solution" but they dont they just try things that don't work as if they have no idea what the problem is. so have they solved this problem yet? I haven't called about it yet because I have had to call so many times about things it is like work to do so and I am not getting paid for it in fact I am paying them. haha. Had to vent here-the survey's don't allow for that. If I get a solution I will post it.