[sdiy] math question - somewhat OT

[Magnus Danielson]

From: Toby Paddock <tpaddock at seanet.com>
Subject: Re: [sdiy] math question - somewhat OT
Date: Tue, 21 Sep 2004 13:41:04 US/Pacific
Message-ID: <200409212041.i8LKf4dX002919 at milkyway.seanet.com>

> (I see it's been answered, but since I already wrote this, I'm sending it 
> anyway)
> I'm probably the last person that should be trying to answer a math question 
> but...
> 
> If you want the linear scale to be octaves:
> 
> For ref_freq being where you want the scale to start.
> 
> octaves= ln(frequency/ref_freq)/ln(2)  
> 
> I THINK you could change the (2) to (10) for decades.

That is EXACTLY what you should do!

You can use log or ln as you feel fit, since the other will correct the
multiplication factor anyway.

ref_freq will be the frequency at origo.

> Someone please correct me if I'm wrong.

The only thing needing correction is the output scaling to pixel-position.

Cheers,
Magnus