Thank you Ingo and Peter for the answer.
About Peter tests what I've is:
1. The tests were made with the jitsi.exe priority in Normal mode, I
felt loss of sound during calls. When I made the test with priority High
didn’t notice any loss. Were made in my laptop processor i5.
2. I made a simple test with a cpu stress program showing no
during a call even with the processor at 100%.
3. Test made with windows media player and windows recorder during
excel processing, no problem in the sound. I didn’t felt any loss.
It looks like some issue between Excel and Jitsi. Any other ideas? Could
be some configuration?