Cross-Spectrum

Smart people's theses

Herb Singleton blog@cross-spectrum.com — Thu, 10 Apr 2008 01:30:00 GMT

While desperately tying to avoid doing actual work, I discovered that MIT has been busy adding student theses to their library website.

Some notable student works (scroll down on the linked pages to find PDF links):

A theory of nonlinear systems by Amar Bose (of Bose Corporation fame)
Systems of urban growth by Nicholas Negroponte (MIT Media Lab and One Laptop per Child)
Sound from ultrasound : the parametric array as an audible sound source by Joe Pompei (Holosonics Audio Spotlight)
The design, development and construction of a low-noise, low-turbulence wind tunnel by Carl Hanson (rail noise pioneer and my former boss/current prime)
Techniques of visual observation of particles in a sound field, Sound scattering from fluid cylinders, and Sound scattering by a cylindrical vortex by Ira Dyer (BBN)
Reducing kitchen appliance noise by Karl Pearsons (BBN)

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Noisy restaurants... again

Herb Singleton blog@cross-spectrum.com — Thu, 10 Apr 2008 01:30:00 GMT

NPR's All Things Considered ran a segment on noisy restaurants yesterday. The story was a follow-up to Tom Sietsema's No Appetite for Noise piece in the Washington Post.

The piece covers familiar ground, but more publicity is always good.

I was a little bothered by the lack of discussion of the role that acoustical experts can play in restaurant design. Take this quote for example:

[Architect Griz Dwight]'s trickiest assignment so far was revamping Black's Bar and Kitchen in Bethesda. Only after a glass-wrapped wine room was in place and a room-length, glass-fronted mural was hung, did Dwight discover that their angles and surfaces bounced noise from one to the other, an effect known as slap-back. To catch the excess sound, the architect hung four box-shaped acoustical panels wrapped in fabric. The design, he half-jokes, is "ninety-nine percent functional, one percent decorative." With a sound level registering about 77 decibels on a weeknight, however, patrons still have to raise their voices.

The soundscape design was left to the architect with unfortunate results. How much did the project owner have to pay for that retrofit? How much business did the restaurant lose because of the noise, construction and/or delayed opening? And how much money could have been saved in the owner had hired an acoustical expert at the start of the project?

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An ode to Mimi

Herb Singleton blog@cross-spectrum.com — Wed, 09 Apr 2008 02:37:00 GMT

MIT alum Liz Burr has been waxing nostalgic on Twitter about the popstar known as Mimi - aka Mariah Carey.

Miss Carey does have a special place in my heart; back in the day I was a huge fan. Friends of mine from my MIT days remember the Mariah poster (a secret Santa present) that always occupied a place of honor on my dorm wall from 1993 to 1995. Not so much today since, well, Mariah went insane back in 2001 and I did what any guy does when a woman goes insane: I ran the other way. Quickly. But from 1990 to 2000, she was more than a star... she was Mimi. Yes, well before she was emancipated.

I got her debut CD Mariah Carey back in 1990 (senior year, HS) as a hand-me-down - my older sister bought the CD, hated it, and gave it to me. I had heard her first single ("Vision of Love") on the radio and didn't have high expectations but I gave the album a chance. Yes, it was the generic mainstream watered-down R & B sound typical of Producer Walter Afanasieff (who also produced Celene Dion's albums in that era), but I absolutely loved it! I didn't even mind Mariah's pathetic attempt at rapping on "Prisoner."

In September 1991 Mariah released her second album just as I started my freshmen year at college. Once again I hated the first single. In fact, I hated all of the singles released from that album, but it didn't matter - Till the End of Time had become one of my favorite songs ever and I would have gladly paid $15 for that one song alone. In fact, I'm listening to that song right now.

I had to wait two years for the next album, but it was worth it. I was pleasantly surprised to find that I really liked the debut single from Music Box. My most vivid memory from the period was the suffering not-so-silently in my dorm room from mononucleosis - that little illness caused me to miss out on dorm rush activities and the varsity football season. As I lay in bed downing painkillers and anti-inflammatory by the bucketfull, the sweet sound of Mariah singing Never Forget You and Music Box helped to ease my suffering. Along with lots of booze.

Daydream and Butterfly were released after I graduated college. As I was moving on in the world, so was Mariah. Walter Afanasieff's influence began to wane as Mariah started producing her own tracks, and collaborating with hip hop impresarios like Sean Combs, ODB, and Jermaine Dupri. Daydream contained the landmark track One Sweet Day with Boyz II Men and Mimi began to make clear her desire to move to a more urban sound. 1997's Butterfly, which cemented the transition was the last Mariah Carey album I purchased.

I'm no longer rushing out to buy her singles (like I said, she did go insane) but in addition to the fond memories I still use the jackswing remix of Someday and Dreamlover as demo songs for audio systems. Both tracks contain heavy bass which can sound sloppy in underdamped systems. I guess I should be amused to find that Mariah has weaseled her way into both my personal and professional lives.

Today I still long for that innocent (to me!) girl belting out those power ballads and flaunting her whistle register. But we'll always have the 1990's... Until the End of Time.

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Classroom sound reinforcement systems

Herb Singleton blog@cross-spectrum.com — Wed, 19 Mar 2008 01:45:00 GMT

Dick Campbell posted this NYTimes article about classroom sound reinforcement systems to the NCAC listserve:

This school year, Wyoming Elementary has equipped every kindergarten through third-grade classroom with the amplification system, technology that was once reserved for large lecture halls or to aid students with hearing or learning disabilities. In an era of chronic ear infections, widespread iPod use and rampant attention-deficit disorders, school officials have embraced the microphones for mainstream classrooms, pointing to research suggesting that all children learn better when they hear instruction loud and clear.

Yes, it's true that kids lean better when they can actually hear and understand the instructional material. But using a sound-amplification system is more of a band-aid than a solution. Proper acoustical design is much more effective and relatively inexpensive if considered during the classroom design/renovation process:

"I'm appalled. This is the triumph of marketing over science," said David Lubman, a fellow of the Acoustical Society who lives in California. "In most cases, they're putting it in as a substitute for good acoustics. In other words, instead of cutting down the noise, they're blasting over the noise, so the net result is more noise."

Some really smart people wrote an ANSI standard that specifies best-practices so you can get it right the first time.

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FTA Vibration General Assessment Utility

Herb Singleton blog@cross-spectrum.com — Mon, 10 Mar 2008 02:13:00 GMT

NTI has scheduled another FTA Noise & Vibration Impact Assessment course for March 18-20 in Oakland California. I won't be helping out this time but Lance will treat you right.

FTA developed (and when I say "FTA developed" I mean "FTA paid NTI who paid HMMH who paid me to revamp") a noise prediction spreadsheet for use in the general assessment phase of the noise analysis. FTA also has a general assessment procedure for rail that involves picking vibration levels for various sources off of plot in the FTA manual. When doing the course vibration exercises I found that I got slightly different answerers each time I worked a problem because I would pick a slightly different value from the plot. To make things easier on myself, I whipped up a small program that provides the reference vibration level for a specific source at a given distance and speed.

Of course I couldn't just build a utility to pick plots off a plot... I spent a little extra time and built an advanced mode that you can use to predict vibration levels using the FTA general assessment procedure. The utility doesn't provide guidance as to how to make predictions; I assume that anyone who uses this utility knows what they are doing. If you don't, please don't try to use this utility - spend some coin and hire a professional. There are some real good ones out there.

This utility is provided AS-IS without warranty of any kind. This utility has NOT been commissioned or endorsed by the Federal Transit Administration. Please direct all inquiries to me.

Download: Mac Version | Windows Version

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