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AudioAcoustics

Serving the Acoustics Community Since 1994

Cross-Spectrum Acoustics Inc. offers Sound & Vibration Consulting Services

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Mar 30, 2003

At 8:00pm last night, the new northbound lanes of Interstate 93 in Boston opened to traffic. I took a ride through the new new tunnel.

It’s different than I expected (much windier than I expected), but overall, I think the project did a good job. I’m sure there will be some bumps (the Boston Globe is reported 6 fender benders during the first full day), and it remains to be seen whether the new highway will stand the test of time. But despite all of the controversy associated with the Central/Artery Tunnel Project, the project staff have a good reason to stand tall. I’m certainly proud to have been a (admittedly small) part of it. Great job people.

Tim Bray says XML Doesn’t Suck, which is not too surprising since he helped to develop XML from SGML. He points out that one of the “XML Does Suck” arguments is that

“XML has a stupid design with two completely different mechanisms for holding content (elements and attributes).”

I agree that the existence of both elements and attributes within XML can make things confusing. Specifically, there is very little guidance that governs when one should use an element vs. an attribute.

The documentation for the Water language tries to provide such guidance. Chapter 2 makes the argument (I’m paraphrasing big time here) that most data should be implemented using attributes. Of course this is contrary to the typical use of attributes for metadata, but then again, I guess all data can be described as metadata for some other superset of data. Is the Water philosophy correct? I don’t know, but I think it’s worth exploring. I may apply this to my Acoustic XML data format and see how it flies.


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Mar 28, 2003

Rob Calhoun reports on the acoustical performance of Apple’s G4 fan noise modification.


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Mar 22, 2003

It was recently brought to my attention that some of the past discussions on this site might be inappropriate in light of some of my past and current relationships. Accepting this advice in the spirit in which it was given, I have edited or removed several items throughout this site. I don’t want to get anyone in trouble.

One of of my current assignments will be over in the next two days (helping out my former employer close finish out one project). I will miss it, but then again I will finally be able to focus my complete attention on Cross·Spectrum. There will be a revamp to this site in the next week or so that will reflect this.

So, what is Cross·Spectrum? First I will tell what it is not: we are not a “full-service” acoustical consulting firm. If you are looking for general acoustical services in terms of developing models, assessing noise impact, or detailed acoustical design, you would be better off going with one of the big boys.

We specialize in acoustical measurements: We offer acoustical measurement services to address situations where a full-service firm may be overkill - high-end home theater, industrial/machine diagnostics, sound reinforcement and more. And of course we can do measurements in support of noise control efforts. We have a broad range of measurement experience (free-field sound, vibration acceleration & velocity, displacement, pressure, quasi-anechoic sound methods, and more) and we can handle most measurement needs at minimum cost. We can meet your needs using COTS and our own internally developed solutions. More on that in the next few weeks.

We can also address two other important needs: we can supplement your existing staff if you are an acoustical firm that finds you are temporarily understaffed, or an engineering or achitectural firm that may not have the necessary acoustical measurement experience. We can also help you to help yourself but providing measurement training, and recommending approapriate tools and techniques for your internal use.

That’s the plan… well part of it at least. You’ll just have to wait to hear the real interesting stuff.


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Mar 19, 2003

I bought a used G4 AGP PowerMac off of eBay a few months back for use as a test server and to run a few (relatively) processor-intensive programs. The machine I bought was well stocked, with a SCSI card, 512 MB of RAM and an ATI AGP DVI card. When I first turned the machine one, I heard the hum of the hard drive and various fans. I thought it was kind of loud, but in the end didn’t think much of it.

A couple of weeks ago, I started to hear a high-pitched whine come from the machine. I figured the hard drive was dying, so I started pricing replacement drives. However, when I opened the machine up while it was running, I noticed that the whine didn’t come from the hard drive - it was coming from one of the expansion cards. Since the ATI card was the only card with a fan, I removed it and restarted the machine. Without the ATI card, the machine was probably 15-20 dB quieter. Yep, the friggin 1-inch fan on the video card was causing all the raquet. Using the stock PCI video card, the G4 quietly hums in the corner.

I got to see David Griesinger talk today at the March GBC-ASA meeting. Dave is a great speaker. He holds some very strong opinions regarding architectual acoustics and the sound quality of opera halls (who else would have the guts to tell Leo Beranek that he’s wrong?!), but he can back it up.

We talked a bit about the need to challenge some of the assumptions that are common in the acoustics community (for example, that a 1.5 second reverberation time is ideal for opera halls). You do see this a lot in acoustics, be it noise control, architectural acoustics, vibration, etc: there are certain long-standing assumptions that we acousticians just treat as gospel in our assessments. Every once in a while, someone needs to stand up and say “hold on, wait a minute.”

I have a new toy to play with: a TerraSonde Audio Toolbox Plus courtesy of Odyssey Pro Sound. So far, I’m very impressed by it’s capabilities (RTA, FFT, signal generator, RT60, PC and Macintosh download software and more). I am also very impressed by their tech support - I sent an email at 11:30pm last night, and got a response at midnight. There are several high-end SLM manufacturers that could learn a thing or two from TerraSonde.

Finally, I have an RSS feed up and running for those who monitor such things.


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Mar 10, 2003

I hope everyone caught last night’s Simpson’s episode. The topic was near and dear to my heart: the flight path the airport has been rerouted over the Simpson’s house, and the Simpsons find the resulting noise unbearable. There is a great quote at the end, something to the effect of “There go the planes right where they should be: flying over poor people’s homes.” Good stuff.


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Mar 08, 2003

Airport owner striking back: “They’ve moved into the domain of the airport, and all they want to do is sit and complain,” said VanSickle, who is taking action to alert would-be residents about the airport in advance of the next housing development. “Isn’t it time to do some planning?”

I’ve joined the 21st century and started using a blogging package, namely Blosxom. It’s simple, it’s portable and it just works!

Now that I’m actually starting up my own enterprise, I need to start thinking about this weblog. Cross·Spectrum Engineering represents a team, while this blog just represents Herb Singleton. I will eventually point the blog over to sonicstorm.com when things settle down, but for now, the two worlds will have to live in harmony.

Okay, I gotta ask: who from Vermont has been hiting my site over the past few days? Not that I mind, I’m just curious as to why this one host keeps showing up in my logs.


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Mar 04, 2003

Well, as of today, Cross·Spectrum is providing noise and vibration measurement services for commercial, municipal, or private needs. If you need baseline environmental measurements, if you need to monitor the noise and vibration generated by construction needs, if you help determine the room response for you home theater, or if you’re just curious about noise or vibration levels generated by an activity, give me a call. I can help.

Maciej Ceglowski has written a response to a Washington Post article that implies that the “old technology„ aboard the U.S. space shuttles is not safe. Maciej’s article points out some of the pitfalls that engineers have in developing systems that must be absolutely reliable, and yet still deliver the impossible. In some ways, this goes back my comments about the Greenbush line. Engineering is about reaching your goals despite limited resources through various tradeoffs. NASA engineers are well aware of these principals. Alas, the same can’t be saif for most non-engineers.


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