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AudioAcoustics

Serving the Acoustics Community Since 1994

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

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Jun 22, 2004

Everyone’s favorite audio company is back in the news again: Bose is finally ready to market their active suspension system for automobiles.

I saw a demo of this system back in 1994. Unfortunately the engineers didn’t give any detailed information on the system, but it seemed to work as advertised. One thing that the article doesn’t mention is that the active suspension also enables the car to take corners much more smoothly. I remember one engineer mentioned that test drivers had to be careful because the system kept the car level even during high-speed cornering — the lack of “feel” meant that the driver could unknowingly push the car beyond it’s cornering limit.

After the demo, I never really thought much about the system until I started learning about the mechanics behind train vibration (PDF, see sections 9.2.5.1 and up). Basically the suspension on a railroad truck is (kinda-sorta-but-not-really) similar to a car suspension, and the unsprung weight of the wheel rolling on rough tracks causes vibration. The heavy mass of the unsprung weight causes the high vibration levels, and the primary suspension resonance affects the characteristics of the vibration.

So what if you could adapt the Bose system for trains? I know, it’s impractical for any number of reasons (cost for one, complexity and durability for another) but if you can actively control the suspension, you could (I think) dramatically reduce the wayside vibration from the train. I think someone at Bose needs to talk to someone at TTCI.

 

Andy Ihnatko of the Chicago Sun-Times has a review of several noise-canceling and noise reducing headphones. The Bose come out on top, but the Shure’s E3c to win the cost/performance contest.


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Jun 18, 2004

I’ve been extremely busy for the past few weeks, so please excuse the lack of updates.

I have two announcements regarding Cross·Spectrum Labs:

 

A resident has taken to the street to protest noise from a nearby industrial source. I’m making note of the article, because it shows that some people sill believe that foliage can “act as a sound barrier.“

In case I wasn’t clear before, let me say it again: trees aren’t sound barriers. Bushes aren’t sound barriers. Shrubs aren’t sound barriers. Hedges aren’t sound barriers. If you want to build a sound barrier, you need something solid — wood, concrete, stone, earthen berms, etc. Seriously, if you can see through it, it ain’t blocking noise. Foliage may act as a great psychological barrier, but it doesn’t stop noise.


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