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AudioAcoustics

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Aug 31, 2007

I can’t believe I missed this: Rick Weiss of the Washington Post wrote a piece about the health effects of noise pollution.

The first thing that jumped out at me about the piece is that a lot of the info in the piece come from European studies and experts. I suppose that reflects the reality that Europeans take this stuff more seriously then we do.

Mr. Weiss also appeared on PRI’s Fair Game to discuss noise pollution.

My one comment about the interview is the part where Weiss claims that noise is “partly in the ear of the beholder.” This line of thought leads to people claiming that noise is “subjective.” Noise isn’t about what you like, it’s about what you find disruptive. I like bird song just as much as the next guy, but when the bird nest next to my bedroom window at my Billerica house kept waking me up at 5:00am, I wasn’t any less annoyed because it was only a bird. “Uplifting music” at 140 dB is going to be just as annoying as harder-edged music at the same ridiculous volume.

My rule of thumb: if a sound interferes with an activity (where activity may be sleep, conversation, quiet meditation, etc), it’s “noise.”

Weiss is right about “control” playing into our degree of annoyances. As Barry Blesser said, we can’t “close our ears” and that leaves us at the mercy of whatever sound environment that is imposed on us.


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Aug 28, 2007

I will be working as an assistant instructor for the National Transit Institute’s Transit Noise and Vibration Impact Assessment Course later this fall in Chicago IL. The 3-day course will cover basic noise and vibration control concepts as described in the revised FTA Transit Noise and Vibration Impact guidance manual, and is designed for transit agency employees, engineers, and consultants. World-renowned rail noise expert Carl Hanson is the principal instructor.

Online registration is available at NTI’s website.


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Writer Garret Keizer is in the process of writing a book about “the politics and history of human noise.” I met him last year at Inter-Noise ‘06 and had the pleasure of spending some time with him a couple of months ago. He recently setup a web site called “Noise Stories” where he invites readers to share their personal experiences relating to noise.

If you have a story to tell, please visit his site and share.


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Lynn Fuston of 3D Audio Inc has posted an MP3 interview with Soundwave Research’s Bob Crowley (full disclosure, Bob is a client of mine).

Pay close attention to the discussion of Chladni. Remember, mode shapes are a function of geometry, not materials.

[via the 3dB forum.]


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Aug 26, 2007

Those of you reading this on the web may have noticed some design tweaks (and of course those of you reading the RSS feed should have noticed nothing). I’ve tested the page on a variety of browsers, but if you notice anything amiss, please let me know.


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I wasn’t going to post about this since the article has appeared in pretty much every U.S. publication over the past week, but when I saw it pop up on Forbes, I figured maybe it was time to comment: Noise Laws Could Muffle Motorcycle Sales. Although it is an AP article, many of the news outlet that published it gave it a headline reflecting the uptick in laws designed to clamp down on noisy motorcycle exhaust systems. I thought it was interesting, but not surprising, that Forbes ( and the Washington Post) looked at it from an economic standpoint.

“And that worries riders rights groups, which fear that a wave of ordinances aimed at muffling Harley-Davidsons, hushing Hondas and stifling Suzukis will create a confusing patchwork of laws that motorcyclists won’t be able to navigate. The motorcycle industry is concerned it could turn these frustrated riders away.”

They’re probably not wrong. But we have to balance the desires of motorcyclists with the desires of citizens to enjoy their communities.

This part has me a little confused:

“The association would rather see an ordinance that targets all vehicles or uses a decibel test to measure actual noise output.

The Council is working with the American Society of Engineers [sic] to establish a sound test that would help equalize enforcement.”

A new motorcycle noise measurement standard? What’s wrong with SAE J1287?


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I mentioned Keith McElveen Sound and Light Reflections blog a couple of days ago. I’ve since had time to go through some of his previous postings - there’s some good stuff there:

Good stuff. Subscribed.


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It looks like the Connecticut Audio Society has risen from the ashes to provide a meetingplace fot CT-area audiophiles.

I’ll have to drop in on a meeting sometime.


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Yet another item on restaurant noise (yeah, I know but they keep coming up!): the NetWell Noise Control blog offers some suggestions to help help restaurants improve their acoustic environment. The term “soundproofing” is incorrectly used in this context (“treatment” would be a better term), but the methodology described in the article is essentially correct.

I would hope that restaurateurs and architects might take their advice, but I’m not going to hold my breath.

(And I promise that will be the last restaurant-related post for the rest of the month.)


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Aug 24, 2007

For some time know It’s been documented in several sources (including the WHO’s Guidelines for Community Noise that excessive noise levels can result in adverse cardiovascular and physiological effects in humans

Now the WHO has apparently gone one step further and claimed that noise pollution can be directly linked “hundreds of deaths” per year because of these effects. However, the Who doesn’t appear to have published their findings yet so details are basically non-existent.


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J. Keith McElveen, a forensic acoustics expert, point me to restaurant noise blog posting a few days back and offered his own perspective on the challenges facing forensic audio practitioners in cleaning up recordings made in noisy restaurants.

When looking at the acoustics of a restaurant I tend to see noise in the aggregate. Keith’s experience shows how the individual sources in the restaurant all have their unique characteristics that must each be accounted for when trying to focus on a specific source. I’m not a forensic expert (I’d love to try it tho’), but I can imagine that the acoustics in these very reverberant and noisy spaces make these projects very difficult.

Of course I can also imagine that mob bosses and other criminals don’t mind so much that their conversations might be hard to distinguish in these public settings…

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Aug 23, 2007

The IEEE Spectrum gives its take on the ongoing loudness war in popular music, complete with visual aides.

While this article is similar to many past discussions on the topic, the Spectrum article goes over the history of dynamic range compression in consumer audio formats and talks about the trade-offs involved in setting the proper dynamic range for a song vs. the listening environment.

Here’s an insightful quote from the article:

Some audiophiles find relief by going back to the past. A few musicians still continue to release their albums on vinyl records (in addition to CDs and online formats). Because vinyl cannot support the loudness that CDs can, these modern vinyl releases are much quieter than their CD counterparts. But they are often less compressed as well, and, in some instances, remastered in a way that is as dynamic as albums released in the 1960s and 1970s.

To this day people are still arguing about the sound quality of the vinyl album vs. the compact disc. What a lot of people fail to realize that is the differences you hear between a song presented in both formats (and there are differences) are not necessarily caused by the limitations of that particular format - songs are often mastered differently for release on vinyl or CD, and the listener is at the mercy of the recording engineer. Just to make things, even more muddled, albums may be mastered differently from CD release to CD release, so your CD of Paul Simon’s Graceland purchased in the 1980’s may actually sound different that a late 1990’s reissue. See this Wikipedia article for an example of this type of “remastering.”


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Aug 21, 2007

The folks at Soundwave Research have been looking at using carbon nanotube-based elements for ribbons microphone diaphragms. As Bob explains on their blog the use of their carbon nanotube elements will allow for lighter, stronger ribbon diaphragms with the net effect of increasing dynamic range, diaphragm resilience and efficiency while reducing the noise floor.

A few months back, Bob gave a demonstration in his lab that showed just how strong the Roswellite ribbons are when compared with their aluminum counterparts: They hooked up the ribbon motor to an AC source and “played” the structure like a speaker using very high voltages, resulting in very high displacements. Most ribbons are in danger of deforming or breaking if you (literally) breathe on them - hence the warning one often sees about not blowing into a ribbon mic. This demo would pretty much destroy most normal ribbons, but the Rosewellite snaps back to its original state when the voltage is removed.

I thought it was a cool demo, but Bob swore me to secrecy and I couldn’t talk about it. Thank goodness they finally released a video of the demo so you could judge for yourself. Given all of the mics I’ve destroyed over the years, I’d love to see the Roswellite used for measurement-quality condensers.


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Michael Bauer posted a follow-up on his blog piece on restaurant noise. In the piece, he asks for a response from restaurant owners about how the soundscape affects restaurant earnings.

One of the comments in the blog post refer to a recent Commonwealth Club discussion featuring noted restaurant designer Pat Kuleto. A couple of bloggers have documented the panel’s response to noise concerns:

“On noise levels in restaurants: All were in agreement that a certain level of noise is good - you want everyone to feel the excitement of being in a place with a lively atmosphere (though, admittedly, it’s a fine line between lively and way too loud).”

“Stoll on noise: Our architects — it’s their fault! [Joke — laughter.] If you have a booked place, it’s going to be loud. You want your restaurant to be busy and exciting.

Honest to God, I want a certain level of noise.”

Well, there you go.


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Aug 19, 2007

In another article relating to my previous post on noisy restaurants, Time magazine published an article last week about soundscapes in commercial spaces:

“Julian Treasure isn’t happy with what he hears. Standing in a coffee bar in London’s Soho district, he’s forced to raise his voice to list the noises bouncing around the café: the rumble of an espresso machine, the hum of a refrigerator and the tinny tones of Michael Jackson through shoddy speakers. To Treasure, it sounds like money slipping away.”

It’s encouraging to see a mainstream publication like Time is acknowledging the importance of soundscapes in public spaces. However, I hope that shop owners don’t misinterpret “pump up the sales volume” as “pump up the volume” - the “right” soundscape at 110 dB is not the “right soundscape.”


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Aug 16, 2007

Hmm, I sense a pattern…

Noisy restaurants aren’t anything new; I’ve written about this topic before, but sadly things don’t seem to be improving. I suppose restaurant owners could be raising the volume to increase customer turnover, but I really think that owners just don’t know any better.

I don’t think that Mr. Bauer is too far off when he wonders about possible lawsuits. I’ve measured sound levels in restaurants and bars and found very high sound levels - high enough that the employees should be using hearing protection. I suspect that a lawsuit or two might wake up restaurant operators.


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Aug 15, 2007

Erica suggested that bloggers should try out the Lijit blog searching service, so I added a Lijit search widget to this page. I think it might need a little tweaking, but so far so good.


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I’ve spent a lot of time this past few months driving all over New England for various projects, all the while relying on my trusty car CD-changer to help relieve the boredom. I’ve gotten tired of constantly switching discs for these various trips so I finally joined the 21st century and bought an iPod adapter (line-level of course!) for my factory radio.

My original intention was to provide access to a greater portion of my music library but all that uninterrupted travel time has provided the opportunity to sample various podcasts. Most of the podcasts I listen to are national and local NPR programs but I’m also trying out various home theater and audio-related podcast programs.

My most recent find is the HDTV Podcast (iTunes link). As you might imagine, the show is mostly focused on HDTV technology with a spattering of media-center and console gaming topics mixed in, but they do discuss audio topics from time to time.

I have to admit that my opinion on the show is mixed. The hosts do provide useful information, particularly in the video realm (I’m especially appreciative of the link to a site with free HDTV test patterns). On the other hand, I found myself disagreeing with the objective criteria they recommend using for loudspeaker evaluation.

Out of the four parameters they list (sensitivity, frequency response, power handling, and impedance) I would recommend not paying any attention to the sensitivity ratings or power handling capacities. It’s true that low-sensitivity speakers or under/over-driving loudspeakers can cause problems but the typical buyer isn’t likely to run into those problems with mass-market products. If you’re buying high-end niche brands (think Wilson) you may run into problems but at that level the salesperson will have enough knowledge to steer you in the right direction. Frequency response and impedance are important parameters (btw, look for a frequency response plot, not just the numbers since they values may be deceiving), but the most important criteria are your ears.

I think part of the issue is that they HT guys are aiming for a less-technical audience so they simplify things quite a bit. However, you can only simplify audio and acoustics so much before the information becomes simply wrong. But for now, I’ll keep listening.

Speaking of podcasts, I think I’ve mentioned before that the GBC-ASA has been making audio recording of the 2006-2007 meetings. We’re eventually going to make those available as podcasts but we have some logistics to work out first. We do plan on recording the 2007-2008 meetings and making those available as well. Stay tuned.


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