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AudioAcoustics

Serving the Acoustics Community Since 1994

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Sep 28, 2003

Going over my referer logs, I’ve noticed that a significant percentage of vistors to this page are looking for information on DIY speaker stands. As a public service, I’m going to list some of the DIY speaker stand designs I’ve come across during my travels around the internet (thanks to Studio Central for some of these links):

Andrew Schmidt (an acquaintance of mine from jobs past) has hooked up with Steve Haas at SH! Acoustics, specializing in commercial and high-end residential audio systems. I’m trying to convince Andrew to give a presentation at a local Boston audio society meeting because they appear to be working with some very innovative technologies.

Yet another intersection of noise and politics: The ACLU believes that a Michigan city’s noise limits may threaten freedoms.

A reader on the Quiet-List asks an interesting question (posted with permission):

As the subject of barking dogs has surfaced, I put a question that has puzzled me for years on end. On more than one occasion, I lived within earshot of constantly barking dogs. I marveled how a dog could bark continuously for over 12 hours, in some instances, without developing vocal chord fatigue or loss of intensity in its bark. Indeed, their unwanted serenade can go on for weeks, even months on end with no diminution or decline in voice. This is remarkable.

Imagine a human yelling at the top of his lungs for even five hours or more. He would be hoarse for days following and even risk damaging his vocal chords permanently. How do dogs accomplish non-stop barking?

Any theories?


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Sep 23, 2003

On again, off again, on again: Greenbush is back. Also, it turns out that the Greenbush line has its own Fan Club.

Kokomo Hum revealed: It looks like Jim Cowan (Acentech) has had some success in hunting down the source of the mysterious Kokomo Hum. This study might make a good topic for an upcoming GBC-ASA meeting.

Paul Roquet is documenting the acoustic ecology of various locations around the world. It’s an interesting perspective of our interaction with sound from a lay point of view.

Macintouch has a report about ripping CD tracks before track 1. It’s common knowledge that the data (music) stream of a Red Book compact disc can be divided into tracks. However, tracks can be further divided using index numbers. Early CD players had a index forward/reverse controls in addition to track forward/reverse controls. However, most studios never bothered to use index tracks on commercial CD’s, so by the early 90’s most CD-player manufacturers stopped providing index controls and displays.

(My 1988 Technics SL-P350 CD player displays the track index, but does not provide index controls. I do own a few CD’s that actually use index tracks - mostly Telarc CD’s).

The Navy is trying to prevent a developer from building a housing development near Oceana Naval Air Station because of noise concerns. Frequently a new noise source is introduced into a residential area, and citizens are often outraged. Here is an example where noisy operations are pre-existing, and the Navy is trying to avoid future noise problems. The Navy is doing the right thing — if homes are built, experience has shown that residents will complain about the noise, even if they were warned beforehand.


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Sep 16, 2003

The Volpe Center has created a Traffic Noise Model (TNM) website containing hints on performing traffic noise analyses using FWHA’s noise model. There is a semi-interesting debate/flamefest in the user forums regarding TNM’s accuracy when compared with the older Stamina model. It’s a debate that I imagine will go on for some time. (For the record I believe that TNM has its problems, but overall it’s an excellent noise model).

Europe’s CALM Network has an online database of transportation noise studies. I’ve heard of some plans to compile a similar database for U.S. noise studies, but nothing this comprehensive.

There’s a new DIY audio site up, and it looks like it has potential. I’ll have to keep an eye on its progress

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Sep 11, 2003

Never Forget


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Sep 07, 2003

Irony: being invited to join the “BanBoomCars” mailing list on the same day I make an upgrade to my car audio system.

Carl Hanson has informed me that the 8th International Workshop on Railway Noise (IWRN8) is being sponsored by the ISVR and is being held in Buxton, Derbyshire in the United Kingdom. If it’s going to be half as fun as the 7th IWRN, I’ll definitely have to attend.


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Sep 06, 2003

Chris Menge of HMMH is in the news for suggesting a noise limit for a race track.

Philip Greenspun has an interesting article on his blog about the death of the compact disc. Philip is a smart guy, and I agree with this general thesis, but some of his statements are a bit misleading. For example, he states:

The encoding system is so badly designed that 80 percent of the bits in the disk’s data stream carry no information, which is one reason that MP3 compression is so successful.

That’s not exactly true - if it were, one wouldn’t be able to hear the difference between an mp3 and uncompressed audio, and yet many people can (now whether most people care about the difference is another question).

He goes on to state:

They forgot to allocate a few bytes for the name of the album or the titles of the tracks on the disk so you have a medium that stores 700 megabytes but not the critical text information that you’d want to see (if, for example, you loaded your CDs into a jukebox).

The original Red Book standard did not allow for such information, but the CD Text feature that was appended to the Red Book standard in 1996 does allow for this. So in other words, the CD format does allow for this, but the record and consumer electronics companies haven’t bothered to support it.

Finally he states:

CDs are so badly engineered that they actually have more distortion than the LP records that they supplanted, especially for classical music (the CD is at its least accurate for very quiet sounds but works great for Heavy Metal). Most serious audiophiles listen to analog LPs or the new DVD-Audio and Super Audio CD (SACD) formats.

Again, this has to do more with CD production then with CD capabilities. CD’s have a 96 dB dynamic range, and most CD-players have 90+ dB of signal-to-noise ratio, compared with ~60 dB dynamic range and ~60 dB signal-to-noise ration for analog LP’s. While CD’s may have problems with recording levels set near the least-significant-bit (which can be partially overcome through dithering), a quiet passage for a CD can be recorded at -70 dBfs which gives plenty of room to adequately capture quiet sounds and still exceed the dynamic range of a typical LP. Of course we still have the problem that many CD’s just aren’t properly mastered.

Philip’s overall point is that the record companies screw everyone, and I agree. However, if the CD is dying, it’s not necessarily because of shortcomings in the format itself - the blame lies in part on the producers that have refused to take full advantage of all the capabilities the CD format offers. Future formats such as SACD and DVD-Audio have the potential so address the shortcomings of the compact disc. But producers and engineers need to do their part to utilize these new formats. Otherwise, garbage in = garbage out, and we’re back to the status quo


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Sep 04, 2003

Another web-based sound level meter demo has concluded. If you’re interested in looking at the reports generated during the demo, you can have a look at the html version or the RSS version.

Science Blog has an article about using disposable microphones to help find survivors located in a collapsed building. Taking this one step further, I could imagine using an array or network of microphones/accelerometers to map out the building structure to locate voids where survivors may be trapped.

I’m trying to gauge interest in a wireless transmitter/receiver system that could be used as a drop-in replacement for long-cable runs in acoustical measurements. Drop me a line if you think this is something of interest to your company and I’ll provide more details.


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Sep 01, 2003

Another noise monitor demo. Note that you need the free Quicktime 6 player and Port 554 open on your firewall to use the streaming feature. You will also need an RSS aggregator to use the XML reporting feature.

It’s nice to spend a Labor Day not flying to Northern California. Although to be fair, I’ve had a pretty good time during during the past couple of Labor Day jaunts to the Bay Area.


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