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Feb 27, 2004

Stephen Dawson has some comments on setting calibration levels for home theater systems. He brings up the point that the normal HT peak level of 105 dB applies per channel. Unless I’m reading that wrong, thats a total peak level of 112 dB, not including the +10 dB (bandlimited) LFE channel. Ouch.


DARPA and NASA are trying to eliminate sonic booms associated with supersonic aircraft: “DARPA and NASA will now work to not just reduce the boom, but eliminate it.”


Ars Technica has posted their Portable headphone roundup which gives subjective impressions of several popular headphone models. They’ve included the reviews of the Etymotic Research ER-6 and ER-4P earphones which have received rave reviews around the web.

Of course this reminds me of something I’ve been putting off for quite some time: I was given a pair of the Bose QC-1 QuietComfort active noise reduction (ANR) headsets as a farewell gift when I left my last jobs (thanks again!). I’ve been meaning to write a full-blown review including subjective impressions and measurement results, but I just haven’t had the time.

Until I do get a chance to make a full report, I’ll leave you with these impressions: has posted a series of articles on “Sound Systems and Human Hearing.” One article (PDF) documents sound levels at an outdoor rock concert.

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Feb 24, 2004

There have been quite a few comments on the web regarding the New York Times article on Bang & Olufsen’s new loudspeaker product (for example, here, here, here, and here among others). In addition to the Dave Moulton designed tweeters, the auto-magic room-equalization function seemed to elicit a lot of comments.

Coincidentally, a thread was started on alt.sci.phyics.acoustics that brings up a relevant point: equalization is useful to tweak system performance, but it can’t correct for gross room acoustics problems. At some point, you need to deal with the room using surface treatments, diffusion, speaker placment, etc. That’s why God created acousticians.


Bill Cavanaugh is quoted in a Newsweek article that discusses soundscape considerations for the September 11 Memorial in New York City.


Didier Depireux answers the question “Do you really hear the sea in a seashell?


It all started with a 15-year-old’s science fair project. The end result is a product that claims to kill mosquito larvae using sound waves.


Nick’s Auditorium chronicles the history of film sound technology, from 1927 to the present.

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Feb 11, 2004

Nissan is deploying a cannon at one of its storage facilities. The cannon emits shockwaves that prevent potentially damaging hailstones from forming (see here for an explanation of the theory). The article claims that the sound level at the cannon is 120 dB (no distance given). I hope Nissan passes out earplugs to the neighbors.

(Thanks Slashdot)


The NASA Lewis Research Center Noise Exposure Management Program is giving away the Auditory Demonstrations in Acoustics and Hearing Conservation compact disc, developed by Hoover & Keith. The disc has demonstrations of various noise sources and hearing impairment conditions. Follow the instructions here to get your free copy.


Audio World has links to application notes that describe surround-sound recording and microphone techniques.


Another story making the rounds concerns noise measurements inside a hospital as reported by the American Journal of Nursing. I know from experience that hospitals can be noisy placed, but 113 dB? I suspect someone has misinterpreted the data, but then again, I wasn’t there.

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Feb 09, 2004

Dolby Labs (of Dolby Digital and Dolby NR fame) is going public.

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Feb 03, 2004

I received the inaugural issue of Multi Media Manufacturer, a magazine geared toward audio professionals. Roy Allison wrote an article describing the “Golden Years” at Acoustic Research. It’s common knowledge that AR founder Edgar Villchur developed the acoustic suspension (sealed cabinet) loudspeaker - what I didn’t know was that Villchur also developed the dome tweeter.

It’s also interesting to read Allison’s impression of the audio market in the 1950’s, 60’s and 70’s. Mounting woofers from the outside of the box was unheard of. Audio engineers didn’t believe that mounting a woofer in a sealed box would work. Turntable isolation systems (which sound more complicated than some railroad track vibration isolation systems I’ve seen!) were used to help reduce distortion. And so on.

The article is fascinating, and I hope that it eventually makes its way to the web. If you are a qualified audio professional, you may be eligible for a free subscription. See the link above.


The Boston Globe has an article about David Moulton’s acoustic lens technology. I’ve seen the prototypes, but unfortunately I haven’t had the chance to hear them.


BTW, welcome to the world Josephine Singleton!

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