Why do my knees sounds everytime I do lunges? It doe not hurt and it can't be result of a sedentary life because I do running and yoga 4 times a week

Patella Tracking. Without an exam of your lower extremities, one cannot with certainty say the cause of the cracking. But my first thought would be a patella tracking problem and/or some asymptomatic chondromalacia patella. If you are concerned you should have a sport's doc or physical therapist evaluated your knee and look at the patellar alignment.
Crunchy kneecaps. The sound is coming from under your knee cap. As you bend your knee, the kneecap becomes more engaged in the knee. This is very common. As long as it doesn't cause pain, try to ignore it. If pain develops, avoid activities that make it worse (eg squats, lunges, stairs, kneeling), ice, anti-inflammatories, and tylenol (acetaminophen). If the pain doesn't improve after a period period of time, call your doctor.