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AudioAcoustics

Serving the Acoustics Community Since 1994

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

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Nov 30, 2003

Famed (some would say infamous) audio reviewer Julian Hirsch died last week. Tom Nousaine wrote this obituary.

Researchers at Ole Miss are developing a method to find buried land mines using acoustics.

Noise in the news yet again: man in China beaten after complaining about construction noise.

findaproperty.com has published a “Beginner’s Guide” about dealing with residential noise issues. The website is based in the UK, but some of the principals discussed are valid in the United States.

Reuters published an article discussing computer noise issues. Nothing earth-shattering, but the article does summarize the difficulties manufacturers encounter that result in noisy machines.


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Nov 22, 2003

Phil Rose claims that a fire originating in his Audi factory speakers destroyed his car. Scary if true.


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Nov 18, 2003

Starting today Cross·Spectrum is offering a new service: Microphone Frequency Response Measurements. The primary purpose of this service is to address the needs of DIY’ers who have purchased low-cost capsules, and want to know the response of their individual microphone. I think it will also be useful to organizations who may want to check the responses of their precision microphones for diagnostic purposes.

Please take note that we in no way, shape or form claim that service represents a NIST-traceable calibration. In particular, our measurement procedure is similar to the “substitution” method, and there will be some inaccuracy at higher frequencies where the acoustic wavelengths begin to approach the size of the microphone diaphragm. Also note that the phase response is determined via Hilbert Transform - the Hilbert Transform is only valid for minimum phase systems, and unfortunately, many microphones are not minimum phase devices. However, we believe this service will help to diagnose problems with microphones at a much lower cost than hiring a calibration laboratory.

The process is pretty simple - send us your microphone and pre-amp, and we’ll run it through our test suite which compares the performance of your microphone with a NIST-calibrated mike. We’ll then send you a summary report that documents the measurement results. We may also be able to give you a calibration file for use with programs like WinAudioMLS, provided we can figure out the file format.

Price for the service is $30US, including return shipping (continental US only), and we accept checks or credit cards via PayPal. We can also make arrangements for oversease shipping. In most cases we should be able to turn around your microphone in 24 to 48 hours. Please contact us for more details.

Update, February 22, 2007:

Please note that pricing for the service, as well as measurement capabilities have changed. See the Microphone Measurement Page and my February 2007 blog post for more information.


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Nov 08, 2003

Time to give credit where credit is due: “Neighbors complain; RTD noise quieted“ — residents complained about noise from an RTD facility (Denver), and RTD did something about it. Good job.

RTD’s actions are an example of one of the best-kept secrets in noise control: a token effort directed at the noisiest activity will often resolve noise complaints. I’m not talking about spending thousands of dollars for noise barriers or drastically readjusting schedules. Often, simple things will help reduce the negative affects of noise, and demonstrate to the community that you are sensitive to its needs.

For example: I worked as a nighttime “noise cop” on a large construction project a few years ago. An ongoing construction activity was located near an apartment building. The construction noise wasn’t particularly loud (it was well within the noise specifications I was enforcing) but it did generate a constant noise that was audible inside the building.

For three nights in a row, a woman in the building called the noise hotline at exactly 11:25pm each night. We did our best to accommodate her, but we were curious as to why she called at 11:25 each night, especially since the activity she complained about usually started at around 7:00pm. The we figured it out: we postulated that the woman came home from work, turned on the television, and kept it on for the night. The noise from the television masked the noise from the construction, and she didn’t notice it! However, she apparently watched the evening news, but turned off the TV after the weather report, which ended at 11:25. When she turned off her television, she noticed the construction noise, and she called the hotline because she feared the noise would prevent her from falling asleep.

The solution was simple. Usually the construction crew took their “lunch” break at midnight. We had them take their break starting around 11:15pm instead. When the woman turned off her television, she didn’t hear the construction activity. The crew started up their work around midnight, presumably when the woman was asleep. Because the noise level from the work was relatively low, the noise was not likely to awaken her. We continued with this schedule for 2 weeks, and had no further complaints.

Again, a simple method that provided an effective solution to the problem at minimal cost and disruption to the schedule. It doesn’t take a lot of effort to be the good guy.

 

The St. Petersburg Times (Florida) is running a profile on the inventer of surround sound. When they say he “invented” surround sound, I assume they are talking about matrixed surround sound, since discrete surround sound had been around in several forms prior to 1967 (Fantasia being one of the prominent early examples).

Diane Carter (another acquaintance from jobs past) is in the news, measuring airplane sound levels to assist in land-use planning.

NoiseLaw.org has set an ambitious goal: “to collect in one place all existing ordinances in the United States.” and in Canada relating to noise in its many forms.


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Nov 05, 2003

Slashdot points to this article from Syllabus magazine, titled “The FREE, 0% APR, Better Sex, No Effort Diet: Syllabus.” The article basically asserts that Free Software and Open Source software are just forms of “the mythical free lunch.” In other words, stay away from open source software because you always get what you paid for.

Where to start? Open source and Free software has made a big splash in the news over the last few years with the emergence of Linux, but the fact of the matter is that open source software has been a staple of computing for at least 40 years. The infrastructure was developed using open source/Free software, and most mail servers and web servers (including this one) are served using open source server packages.

So why should you care about open source software? Frankly I don’t know; but I can tell you why I care about open source software: it gives me alternatives. Better yet, it allows me to perform my required computing tasks such as typesetting, numerical processing, plotting and GIS at comparable quality and much lower costs than proprietary alternatives. Not bad for $0.

I’ve used open source software to build robust data analysis systems that have significantly reduced analysis time and provided increased flexibility. These systems would have cost several thousands of dollars to implement using proprietary systems, while providing little increase in quality. This has both increased efficiency for projects I’ve worked on, and saved money for my clients.

Now I’m not trying to say that open source software is suitable for all tasks; it’s not. In fact my primary computers run the “non-free” Mac OS X operating systems and my data loggers run Windows. But in choosing these platforms, I considered alternatives like Linux, and NetBSD and picked what was cost-effective for me.

So if you feel the need to drop big money on proprietary software without considering the alternatives, go right ahead — it makes it that much easier for me to compete.

 

An editorial from the News-Press (Fort Myers, FL) has the guts to say what is on the mind of many: “Hate noise? Don’t build near airport.

The New York City council takes note on NYC’s noise problems. The article makes specific reference to New Yorks subway system. It may not be common knowledge, but New York City Transit actually does a lot of work to reduce noise and vibration on their system. Noise levels could be lower, but considering that the system has 650+ miles of track and several hundred vehicles, NYCT is doing pretty well with limited resources.


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