tone() fails under 31Hz [imported]

This is [Issue 558](http://code.google.com/p/arduino/issues/detail?id=558) moved from a Google Code project.
Added by 2011-06-10T14:31:23.000Z by [adrianra...@gmail.com](http://code.google.com/u/111357028418552252670/).
Please review that bug for more context and additional comments, but update this bug.

Original labels: Type-Defect, Priority-Medium
### Original description

**What steps will reproduce the problem?**
1. Call tone(13,31). You will see a very fast blinking on the LED.
2. Call tone(13,30). You will see a seemingly continuously lit LED (it actually is a very high frequency blink).
Any frequency below 31Hz will reproduce the problem.

**What is the expected output? What do you see instead?**
Expect to see the correct frequency, but a much higher one is seen instead (using an oscilloscope). Also observed on other digital pins.

**What version of the Arduino software are you using? On what operating**
**system? Which Arduino board are you using?**
Tried on Arduino UNO and Nano with ATMega328,
using Arduino 0022 on linux.