Temperatures, Cooling and Noise
The Acer Aspire S7-391 is quite thin, meaning it has very little room for cooling fans or heat sinks. Normally a system of this size would run a bit on the hot side. It's also got the faster, and as a byproduct, hotter Intel Core i7 processor.
As you can see, on the front of the system, we logged a maximum temperature of 101 degrees Fahrenheit. This high temperature was located above the keyboard and somewhere you are unlikely to touch during normal use. The keyboard stayed below 90 degrees and the palm rests stayed under 80 degrees.
Moving around to the back side, temperatures were slightly worse. The maximum observed temperature was 108 degrees Fahrenheit. The rest of the system ranged from 81 degrees to 105 degrees Fahrenheit. These temperatures are a bit higher than I would like to see for a system to be used on my lap.
The maximum observed GPU temperature was 83 degrees Celsius, which is the same as the CPU because they are on the same die. The CPU reached a maximum of 83 degrees Celsius, a temperature that is a bit better than I was expecting going into this test. It's well within the limits of the CPU / GPU and should cause no long-term damage to the system.
The Acer Aspire S7-391 produced a sound level of 51 decibels in our measurement. Due to its small size, the fans had to work extra hard to move enough air to keep the system cool. Our measurement is taken in front of the laptop at roughly head level. For comparison, 30dB is a totally quiet night time in the desert, 40dB is whispering and 60dB is a normal conversation.