On my computer (and also on my second computer) I found out that some smart-FAN features (not only cool 'n quiet or speedstepping) create non-latency/ performance related small clicks once every while.
Many BIOSes these days have ways to regulate the FAN/ CPU speed. Aside from speedstep (intel) and cool’n quiet (amd) there aren other BIOSes out there with other extra options like smart/ or Q-FAN options which you can also set to a specific profile (i.e. silent, standard, performance, etc.). I found out that apart from changing clock frequencies these settings also create small dips in the motherboard 5v/12v power lines due to switching of FAN speeds and temperature measurements/ interpretation.
My tip: Let the FAN run full speed and regulate it with a variable resistor or something else. Any form of intelligence/ temperature measurements/ switching of FAN speed/ Core-downs/ Speedstepping will affect the sound quality one way or another (being latency issues or in this case other more hardware related artefacts).