Hot Hardware published a review on the NVIDIA's Whisper Mode For GeForce-Powered Gaming Laptops Put To The Test A quote from the article:

A new feature of NVIDIA's latest GeForce technology for laptops that we weren't able to fully evaluate until now, is something NVIDIA calls Whisper Mode. Like its recently introduced Max Q technology that paves the way for thinner and lighter gaming laptops such as the ASUS ROG Zephyrus GX501, Whisper Mode is another type of mobile gaming optimization, except it focuses on noise output with the intrinsic benefit of lower power draw as well. Short and to the point, it is an intelligent framerate pacing technology designed to lower GPU power consumption, utilization, and ultimately fan noise, while still delivering a smooth and playable gaming experience...

 NVIDIA's Whisper Mode For GeForce-Powered Gaming Laptops Put To The Test @ HotHardware