Noise Analysis: Frequency Spectrum And Videos
Let’s start with a task that features a continually-changing load, never reaching 100% or falling below 40%. We begin our video analysis with a round of Crysis 3. You’ll hear the card start whining at the five-second mark.
Since the fans start off quietly and only become audible toward the end of our video, we want to concentrate on the parasitic noise that dominates throughout the recording. The fans aren’t responsible for this card’s noise levels at all. A frequency spectrogram helps us to understand this better. Its color scale represents the individual levels ranging from blue (quiet) and purple (middle) through red (elevated noise levels) to orange and yellow (loud). Green stands for the predetermined upper limit, which is never reached:
The fans only kick into high gear when a compute-heavy app pushes both Tahiti GPUs to full load, filling in the lower end of the frequency spectrum. This makes them seem louder to human ears, as if they were responsible for the overall noise level. A video helps us illustrate once again.
And here’s the spectrogram that goes along with the video. It shows us how the fans easily drown out the whining under full load.
We’ve learned two things. First, as a result of the components generating noise at different frequencies, AMD’s Radeon HD 7990 cannot be accurately measured using a simple sound level meter. Second, AMD partly undermines the hard-earned progress that went into quieting its cooling solution. Although the overall result isn’t bad (we’re certainly much happier with the 7990 than the 6990), the high-pitched whine is noticeable enough to illicit raised eyebrows from observers correctly ascertaining that a graphics card shouldn’t be making those noises.
Reference Under Load: GeForce GTX 690
To give you a point of comparison, we applied the same load to GeForce GTX 690 and recorded its output.