80-90% is a 1.27 times increase, 90-100% is 1.23 times. However there are various extraneous issues that affect the results.
For example, The human ear's sensitivity to sound (which is also logarithmic) will at different sound pressure levels display varying sensitivities to a given frequency in a way that doesn't seem logical, and is related to its physical construction.
Another issue is the whistles and such that may only resonate at higher wind speeds, for whatever reason.
Then there are bearings, that get unduly noisy with a certain amount of pressure (lubrication issue or whatever).
For example, The human ear's sensitivity to sound (which is also logarithmic) will at different sound pressure levels display varying sensitivities to a given frequency in a way that doesn't seem logical, and is related to its physical construction.
Another issue is the whistles and such that may only resonate at higher wind speeds, for whatever reason.
Then there are bearings, that get unduly noisy with a certain amount of pressure (lubrication issue or whatever).