May 30, 2005

Music Thing has published histories of the THX sound and the Macintosh startup sound.

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Newsweek magazine is running a cover story this week on noise-induced hearing loss:

Of course, noise isn't the only culprit. "Even if you spent your life in the library, you wouldn't hear as well when you're 70 as you do when you're 20," says Dr. Robert Dobie, professor of otolaryngology (ear, nose and throat) at the University of California, Davis. But who spent their lives in the library? Not Kathy Peck and her fans; not the folks riding jackhammers on road crews, and not the firefighters and cops dashing to the rescue with their sirens screaming. Even pediatricians have been known to develop hearing problems after years spent around crying babies."

[Tag: Hearing]

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Product & Research News:

• A Boston University graduate student has developed an underwater acoustic sensor array based on off-the-shelf components to aid in national security efforts.
• Applied Minds, a California firm founded by a computer architect and an industrial designer, is marketing an "electric silencer" to help guard privacy in open office spaces.
• Students at Western New England College got a close look at technologies used to suppress aircraft engine noise.
• The Tampere University of Technology has developed "The Noise Shirt" to help alert workers to excessive noise exposure. [via engadget]

[Tag: acoustics]

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Recent articles of note from Home Theater Blog:

• My about face on extended warranties: "We now all but insist new flat screen purchases included an extended warranty and if the customer declines, we bluntly inform them of the consequences. This may seem a little harsh, but we're not talking about $300.00 DVD players that can be considered almost disposable, in the scope of a larger project. We're talking about a display that on average sells for four thousand dollars or more."
• Smaller, intimate home theaters: "Don't get me wrong, I'm not complaining, it's just that often these 40x60 monsters are owned and used by families with 4 or less members. Not surprisingly the construction based on square footage alone, often exceeds all other costs combined."

[Tag: Home Theater]

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May 10, 2005

Short takes, some old, some new:

• Are your noisy neighbors bugging you? Get some payback!.
• From NewScientist.com: Non-acoustic sensors detect speech without sound
• I had asked before about a report indicating that idiots enthusiasts are mounting train horns on cars. Looks like it’s true.
• There are lessons to be learned, both technical and political, in this story about an ill-fated noise barrier.
• Sound control as art: Sound-Dampening Cardboard Wall Sculpture. It would be nice to see some 3rd-party test results.
• Perhaps there is a rational explanation for lip-synching at live events? (Other than ‘the performer can’t sing,’ obviously.)
• From ABC News: Hearing Loss: A Preventable Problem.
• Interesting confluence of thermodynamics and acoustics: Exhaust heat powers car’s air-conditioning
• Time to tune up your ears and Learn to Listen
• Matt Bartlett has expanded his webpage to encompass other DIY audio projects.
• A little while back, I got curious about the hearing response of dogs, and found this page which gives audiograms for several different animals.
• “Hey, now, what’s that sound” – Security software recognizes the sounds of danger.
• Professor J Kim Vandiver is being honored for his service to the oil industry. Professor Vandiver is both an excellent instructor and a valuable resource - the award couldn’t have gone to a nicer guy.
• Listen Carefully, House Hunters, and Plan Ahead: “Before you think about noise inside the house, check the surrounding environment, advised Savereid, who’s gotten more than one phone call from a distraught home owner who moved in and then discovered his house was in the flight path of an airport.”

[Tag: acoustics]

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May 03, 2005

This past weekend, I got to do something that I've never done before: I recorded an organ recital performed by Dr. Leon Tilson Burrows and Karen Whitney at Springfield's Old First Church. My recording setup consisted of my Marantz PMD670 solid state recorder and two ribbon microphones in a stereo Blumlein configuration (the microphones are not generally available yet, but if you're interested in them, I would suggest that you watch this space over the next couple of days). While I have probably made dozens (if not hundreds) of audio recordings for noise control and diagnostic purposes, but this is the first time I've attempted to make a music recording. I discussed this effort with several friends and colleagues, many of whom shared stories of 'professionally-made' recordings that did not come out well. No pressure.

All-in-all, the recording came out fairly well. The biggest problem came about because of my choice of microphone placement. If you click on the picture above, you'll see that the microphones are only located a few feet above the proscenium floor. I didn't want the microphone stands to block the line-of-sight between the audience and the performers, so that limited my choice of mic placement. As a result, footfalls on the stage and on the organ pedals were audible throughout the recording.

I spent yesterday preparing a CD of the recording - the basic steps included down-sampling from 48kHz to 44.1kHz, applying compression, applying gain to some of the annotations, and editing 'dead air.' Some lessons I learned:

• As a sometime-audiophile, I've always advocated the practice of keeping recordings as 'pure' as possible, with no compression or equalization added during or after the fact. Turns out, compression is a necessary evil. The dynamic range of a live performance is just too much to be useful in even a high-end system in all but the quietest of listening rooms.
• The above observation has confirmed in my mind that more than 16 bits of dynamic range for playback in a consumer audio system is just a waste - again, unless you have a very quiet listening room (and like your peaks to be extremely loud), you would never use all of the dynamic range. That said, there is such a thing as apply too much compression. (None of this, of course, applies to recording and mixing, where 24 bits or more may be necessary to properly capture and edit audio signals.)
• I performed the digital audio processing using the free, open source Audacity audio editor running on Mac OS X. I'm a big fan of open source and free software (my business practically runs on TeX, MySQL and GNU Octave), and I've found Audacity useful for rudimentary audio editing. It's been argued that Audacity is suitable for professional audio use, and this project gave me a chance to put it through its paces. Long-story short: Audacity is nice, but it's not a pro tool (pun intended). Audacity has lots of quirks, but the bug that made be give up on it was when its "save multiple" function (for splitting one track into separate files) placed the same audio samples at the end of one track and at the start of the following track. Audacity is nice, and it will get better with time, but it's not there yet.

These are certainly not earth-shattering insights for experienced recording engineers, but it is interesting to walk in their shoes for a bit.

[Tag: recording]

ExtremeTech has published an outstanding article on THX's approach to providing a great sounding audio system. I'm particularly happy that both THX and the article stress the important of room acoustics to the overall sound. My only complaints with the article are that the author confuses resonance with modal behavior, and that he confuses the effects of absorption and diffusion.

[Tag: acoustics]

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