Have TV Questions? Ask a TV Technician
Hello, The cable company can only determine the problem is not coming down the cable line. They cannot determine, however that the issue is not being caused by the box. Now, when you say "you lost sound for a few seconds on different programs", this leads me to think its the cable box- as opposed to the TV.
However one test you can try that will tell you WITH CERTAINTY if the issue is the cable box or TV, is to try another source- such as a DVD player. If the DVD player playing through the TV does NOT have this same sound- then the problem is not with your TV- it is with your cable box, OR HDMI cable and you would then want to have the cable company swap out their cable box.
Alternatively, if you find the issue ALSO occurs with the DVD player, or you've already swapped the Cable Box and HDMI cable, then I would need the model number off of the back of the TV and the AGE of the set to be able to help further.
If you need further assistance let me know. Please do not forget to click a POSITIVE RATING before you go- as it's how I am credited for my work. You can follow up at any time, at no additional cost.