# Exponential curve for¶

notes
```When you design a frequency control for your filters you may need an exponential curve to
give the lower frequencies more resolution.

F=20-20000hz
x=0-100%

Case (control middle point):
x=50%
F=1135hz

Ploted diagram with 5 points:
http://img151.imageshack.us/img151/9938/expplotur3.jpg
```
code
 ```1 2``` ```//tweak - 14.15005 to change middle point and F(max) F = 19+floor(pow(4,x/14.15005))+x*20; ```

```same function with the more friendly exp(x)

y = 19+floor(exp(x/10.2071))+x*20;

middle point (x=50) is still at 1135hz
```
```Here is another function:
This one is much more expensive but should sound more linear.

//t - offset
//x - 0-100%
//y - 20-20000hz

t = 64.925;
y = floor(exp(x*log(1.059))*t - t/1.45);

Comparison between the two:
[IMG]http://img528.imageshack.us/img528/641/plot1nu1.jpg[/IMG]
```
```Yet another one! :)
This is one should be the most linear one out of the 3. The 50% appears to be exactly the same as Voxengo span midpoint.

//x - 0-100%
//y - 20-20k

y = floor(exp((16+x*1.20103)*log(1.059))*8.17742);

//x=0, y=20
//x=50, y=639
//x=100, y=20000
```