PIPO X12 fan with noise sometimes?

As the temperature is more and more higher in Summer, the electronic device will with a little more hot than usually. Many customers has asked the question that whether it comes with a small fan to cool itself. There are only the model of the PIPO X12 and the PIPO X10 Pro come with the built in small fan. But what we want to remind is that when the device with a higher temperature that the speed of the fan will be quicker then it will produce the noise, when the temperature is down, and the noise will be disappeared, that's the reason why we hear the noise sometimes.