Yusuf’s blog supplemental

howto → Howto: Vuvuzela filter using Linux (Ubuntu)

June 15th, 2010 by Yusuf

By now there are more than a few bog posts like this on how to filter out the resonant frequencies produced by the vuvuzela.

I wasn’t too happy with any of them and thought I’d share what I came up with after some tinkering.

For the impatient:

To install required tools:

sudo apt-get install sox

To test:

play vuvuzela.wav vol 0.9 bandreject 116.56 3.4q bandreject 233.12 3.4q bandreject 466.24 3.4q bandreject 932.48 3.4q bandreject 1864 3.4q

The test file can be downloaded here.

My starting point for this was a post by Russell Beattie, where he describes his attempts at using SoX.

You can test both approaches (using an equalizer vs. using a band-reject filter), and I think the latter does a better job. I also used slighty more accurate frequencies as suggested here and added an additional lower resonant frequency at 116.56 because I could still here a faint toot.

Russell chose to use Octave to define the width around the central frequency that is removed (.1o), whereas I prefer using the Q-factor as did the original German Blog post on this subject (3.4q)

To use:

rec -d|play -d vol 0.9 bandreject 116.56 3.4q bandreject 233.12 3.4q bandreject 466.24 3.4q bandreject 932.48 3.4q bandreject 1864 3.4q

Assuming your default sound input source is the your line-in or tv-tuner.

Updated: I updated the fundamental and harmonics as per this site.

Updated again: The above update should have been better, theoretically, but it isn’t.

Vuvuzela Frequencies

Fundamental: 232.4 Hz

Harmonic 1: 464.8

Harmonic 2: 697.2

Harmonic 3: 929.6

Harmonic 4: 1162

Harmonic 5: 1394.4

Harmonic 6: 1626.8

Harmonic 7: 1859.3

Tags: Linux, ubuntu, world cup

Uncategorized → How-To Recover password under Ubuntu — Ubuntu Geek

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November 27th, 2007 by Yusuf

How-To Recover password under Ubuntu — Ubuntu Geek: “If you forgot you password for your ubuntu system you can recover using the following steps Turn your computer on. Press ESC at the grub prompt. Press e for edit. Highlight the line that begins kernel ………, press e Go to the very end of the line, add rw init=/bin/bash press enter, then press b to boot your system. Your system will boot up to a passwordless root shell. Type in passwd username Set your password. Type in reboot”

Tags: Linux

Uncategorized → Linux evolves for mobile phones

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May 8th, 2007 by Yusuf

Ubuntu on a mobile! I can’t wait….

“The Ubuntu Mobile and Embedded project aims to create the open source platform for initial release in October 2007.

The operating system will be developed by members of the Ubuntu community, along with staff from chip giant Intel.

Its development was prompted by the growth of power hungry portable devices that place new demands on software.

“It is clear that new types of device – small, handheld, graphical tablets which are Internet-enabled – are going to change the way we communicate and collaborate,” said Ubuntu CTO Matt Zimmerman.

“These devices place new demands on open-source software and require innovative graphical interfaces, improved power management and better responsiveness.”

Mobile firms such as Nokia are already using open source technologies in some of its products….”

Tags: Linux, Mobile