The output y performs a logarithmic frequency sweep.
The logarithm of frequency w performs a linear ramp from log10(wMin) to log10(wMax).
It uses wMin*(wMax/wMin)^x instead of the equivalent 10^(log10(wMin)+log10(wMax)-log10(wMin)*x) to help with unit-checking.
The output is the decimal power of this logarithmic ramp.
For time < startTime the output is equal to wMin.
For time > startTime+duration the output is equal to wMax.