Time and frequency in loudspeaker measurements by Richard Heyser

Monday, September 20th, 2010

by Richard C Heyser

I recently came across an article that describes the duality between time and frequency. In most descriptions of the the topic, the math gets heavy very quickly and it isn’t easy for the dedicated reader to keep up. This article is interesting because it attempts to keep the discussion in a more subjective domain.

I found the article a number of months ago when I was searching for a way to take acoustic measurements in less than ideal conditions. Richard Heyser pioneered Time Delay Spectrometry, a method that can eliminate the influence of room reflections from audio measurements. I didn’t expect to find a number of articles, also by Heyser, about modeling subjectivity in audio. I ordered the anthology of his work and found his discussions fascinating. (You can find the anthology further down this page.)

If you are interested in frequency and the nature of the Fourier transform, but haven’t managed to get much out of it, I recommend that you check it out. The article was originally published in Audio magazine which quit operating in 2000. If you find the article interesting, I highly recommend that you order the anthology too.

Quick and easy binary to dB conversion

Sunday, August 22nd, 2010

Here’s a trick to easily and cheaply convert from a binary number to decibels. Depending on your application, the algorithm can be made even more simple.

Writing and scribbling all over your .pdfs

Thursday, July 8th, 2010

I find it easier to read off of a screen if I can scribble on the document, adding my own notes and ideas. There’s a program called Foxit Reader that lets you do that. The free version does everything that I need it to do.

Setting up a TFTP server in Ubuntu

Tuesday, June 22nd, 2010

It’s pretty simple

Defeating writing challenges

Tuesday, May 13th, 2008

I found the writing portion of my PhD difficult. The words slip easily from my mind onto the page while writing for myself. However, I often found myself blocked while writing the dissertation. At times, putting words onto the page felt almost painful. Below, I describe how I overcame this challenge.

I like to analyze and understand everything. However, one of the things that I came to realize is that I don’t understand the writing process. I don’t understand how I convert ideas into words. When I attempt to analyze writing, the writing stops. Analysis may be fine in the later editing stages but I find analysis deadly to the process of synthesizing new text. While writing, I have to force myself let go of my impulse to analyze and to write without trying to write.

I also have a tendency to focus on problems and details. I like to ensure that I have covered every possible issue and exception. As a result, I tend to focus in on problematic details, forgetting the context of the entire work. This results in blockages within the writing process. To reduce my focus on problematic details, I exported notes that I had made out of the main document and into a separate file that I don’t see while writing. I also forced myself to skim the entire work each day to remind myself of the big picture.

Here is my personal list of techniques. Keep in mind that everyone writes differently. While I found these techniques helpful, the same techniques may or may not work for you.

  1. Trust that the process of writing will, sooner or later, result in something good. It’s not necessary to understand how ideas are converted into words. Just sit down and write and see what happens. The act of writing is an act of faith and analysis shuts down the writing process.
  2. Write what you know and keep it simple. Don’t try to write beyond your knowledge. Just write what you understand and write it as clearly as possible.
  3. Keep working on a creative project that generates new content, even if only a little time each day. This creative work will feed into and accelerate the writing process. Writing 100% all day every day leads to burnout.
  4. Know that the core ideas meet or exceed the requirements of the final product. This makes the writing go smoothly. You don’t need to understand how ideas are converted into words. You do need to understand the ideas themselves.
  5. Realize that other people probably have lower expectations than you do. Don’t aim for perfection. Just write.
  6. Gloss over problems and gaps in the main document as though there is no problem at all. Present everything in the best light possible, as though anyone could read it tomorrow and feel like it is complete. If you have to, keep a list of notes in a separate document that you don’t see while writing.
  7. Do not put notes in the document. Extra notes create blockages in the writing process as the mind focuses on fixing problems rather than writing. Extra notes also bring problems to the attention of reviewers. This distracts them from the writing that you have already completed. If something is missing, let them bring it to your attention. Keep extra notes in an extra file that you don’t see while writing.
  8. Skim the entire work daily. This provides context. It will prevent you from writing in a way that does not fit into the rest of the document.
  9. Freely delete low quality material. Holding onto junk text will block the writing process. If you can’t bear deleting, cut and paste that material into a separate document that you won’t see while writing.

    Two more points for techies…

  10. If you are using an editor such as latex, make sure that you can easily see, navigate and edit the product in its final form. When reading the final product, you will see things that you cannot see in the editor.
  11. Use source control so that you can easily delete or rewrite low quality work throughout the document, knowing that you can always get it back.

These techniques were helpful to me and they may be helpful to you. If you would like more ideas about defeating writing blocks, I highly recommend Understanding Writing Blocks by Keith Hjortshoj.

The Sons Of Martha by Rudyard Kipling

Tuesday, July 10th, 2007

Engineers read the following poem while initiating students at iron ring ceremonies.

The Sons of Mary seldom bother, for they have inherited that good part;
But the Sons of Martha favour their Mother of the careful soul and the troubled heart.
And because she lost her temper once, and because she was rude to the Lord her Guest,
Her Sons must wait upon Mary’s Sons, world without end, reprieve, or rest.

It is their care in all the ages to take the buffet and cushion the shock.
It is their care that the gear engages; it is their care that the switches lock.
It is their care that the wheels run truly; it is their care to embark and entrain,
Tally, transport, and deliver duly the Sons of Mary by land and main.

They say to mountains “Be ye removèd.” They say to the lesser floods “Be dry.”
Under their rods are the rocks reprovèd—they are not afraid of that which is high.
Then do the hill-tops shake to the summit—then is the bed of the deep laid bare,
That the Sons of Mary may overcome it, pleasantly sleeping and unaware.

They finger Death at their gloves’ end where they piece and repiece the living wires.
He rears against the gates they tend: they feed him hungry behind their fires.
Early at dawn, ere men see clear, they stumble into his terrible stall,
And hale him forth like a haltered steer, and goad and turn him till evenfall.

To these from birth is Belief forbidden; from these till death is Relief afar.
They are concerned with matters hidden—under the earthline their altars are—
The secret fountains to follow up, waters withdrawn to restore to the mouth,
And gather the floods as in a cup, and pour them again at a city’s drouth.

They do not preach that their God will rouse them a little before the nuts work loose.
They do not preach that His Pity allows them to drop their job when they damn-well choose.
As in the thronged and the lighted ways, so in the dark and the desert they stand,
Wary and watchful all their days that their brethren’s ways may be long in the land.

Raise ye the stone or cleave the wood to make a path more fair or flat;
Lo, it is black already with the blood some Son of Martha spilled for that!
Not as a ladder from earth to Heaven, not as a witness to any creed,
But simple service simply given to his own kind in their common need.

And the Sons of Mary smile and are blessèd—they know the Angels are on their side.
They know in them is the Grace confessèd, and for them are the Mercies multiplied.
They sit at the feet—they hear the Word—they see how truly the Promise runs.
They have cast their burden upon the Lord, and—the Lord He lays it on Martha’s Sons!

– Rudyard Kipling

I often feel this way:

They do not preach that their God will rouse them a little before the nuts work loose.
They do not preach that His Pity allows them to drop their job when they damn-well choose.

I often feel like there are many things that I have to do before I can have fun, that if I don’t do my job, the world might fall apart. I would prefer to be more like a Son of Mary, able to just enjoy of life.

For me, Kipling’s poem captures my feelings of conflict between engineering that is often subject to strict constraints and artistic expressions that seem more free. That said, the dichotomy is not entirely true. There is a joy in engineering technology. It’s fun to figure out how technology works and to create things using that knowledge. Besides, art isn’t entirely free. It’s a hell of a lot of work to carry out an artistic project of any consequence.

The assumed segregation between art and engineering has annoyed me for a long time. That’s why I’m happy to see projects that bring the two approaches together.


Friday, May 11th, 2007

This is old news but if you’re stuck with a lousy selection of fixed-width fonts in Windows XP, you might want to take a look at Consolas, a new fixed-width font that comes with Microsoft Visual Studio and Vista. It’s a big improvement on Lucida Console and Courier New.

…2007 May 15

It looks good on my laptop but not as great on another desktop that I tried.

Consolas was designed to work with ClearType, which I have been using for a couple years. For that reason, not everyone likes it.

If you have XP, you can get Consolas at least three ways:

Orwell on writing

Monday, June 5th, 2006

Entertaining and opinionated writing advice from George Orwell.

On Writing

Wednesday, March 1st, 2006

I finally finished reading Style: Toward Clarity and Grace by Joseph M. Williams. I talked about this book at an earlier time on this site. The book starts by talking about what to do rather than starting with rules of grammar. By focusing on the goals of writing, it becomes easier to write and learn without becoming blocked by fear of grammatical error. Williams saves the “rules” for the last chapter where grammar becomes more about refining the style of writing.

I also finished reading On Writing by Stephen King. I found it entertaining and easy to read. King’s book is mostly about his life as a writer and his attitude and approach to writing. He has some good tips too.