Welcome to Audio Anecdotes

Three VolumesAudio Anecdotes is the title of a community contributed Audio Cookbook in the spirit of Andrew Glassner‘s classic Graphics Gems series.

Please read our article solicitation, and topics list, to get a better idea of what is coming and how you can help.

If you are interested in contributing articles (see author’s guide), have questions or suggestions please contact me, Ken Greenebaum!

Sound is such an important part of our lives, and should get more attention in the computer space (in user interfaces, games, data mining, etc.) This book fills a wonderful void in providing a lot of small, introductory articles, useful for anyone interested in computational sound.
Perry R. Cook, author of Real Sound Synthesis

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Received my Doppler Labs Here T-Shirt

But I really want the device!

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Doppler Here. Where? Kickstarter…


A hearing aid for the rest of us?  No, don’t tell the FDA, but read on.

When I learned that Gints, an old SGI buddy and fellow signal processing advocate joined a small started called Doppler Labs I was curious so I visited their website and learned about Dubs their only product (earplugs with equalization provided via computer designed mechanical baffles tuned for listening to loud live music without damaging your hearing or the integrity of the experience).  Cool product, but how does that relate to Gints, an embedded DSP expert?

Recently I stumbled across Doppler’s Kickstarter campaign for their new product, confusingly called “Here”, and I began to understand Gints’ move. Here is an active, DSP based earplugs with impressive sounding capabilities that allow you to selectively tune in what you are listening to and tune out what you are no by providing:

  • a tunable equalizer providing 25 dB of attenuation and up to 5 dB of amplification
  • tunable active noise cancelation
  • effects!? (this band would be perfect with a little flange?)
  • all controlled in realtime via an iPhone companion app
  • in a pair of small, rechargeable, not too unhip looking packages

Frankly I am unsure what to make of Here, but am eager to give it a try and consequently ponied up the $199 Kickstarter funding level (the early bird specials had already flown)

Check Here out and let me know what you think…

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The loudest recorded sound?

The loudest sound recorded in the annals of history if not recorded on actual audio gear was apparently the 1883 Krakatoa volcanic eruption according to Aatish Bhatia’s fabulous article.

Some outtakes:

  • The sound was 172 dB SPL 100 miles away based on a barometer measuring the pulse at 2.5 inches of mercury
  • Sound waves (the compression and rarefaction of the atmosphere) top out at 194 dB SPL, in the Earth’s atmosphere, because at that SPL rarefaction leads to a vacuum, the limit of what is possible. Pressure waves above 194 db SPL simply push the molecules around and are considered shock waves.
  • The sound continued to reverberate around the globe (as measured by instruments) at roughly 34 hour intervals (the time required for sound to circumnavigate our planet.
  • The sound was observed by people up to 3000 miles from the island of Krakatoa

Aatish includes a link to a video recording of a relatively small eruption where the observation of the eruption was followed by a visible expanding shock wave with the over pressure eventually hitting the camera and the folk recording.

A list of high SPL sounds for comparison.

The story is not simply a curiosity but also a great tragedy as over 100,000 people may have perished in the eruption and resulting tsunami.

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See you at Maker Faire Sunday

mfheader477x109Yell if you want to connect with me at Bay Area Maker Faire this Sunday!

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Parallella Arrived!

Kudos to the Parallella team for shipping! I just received my Parallella and now need to find some time to power it up and find an interesting project. Soft Radio here I come?

Just to recap the parallella is a $99 board featuring the Epiphany 16 (or 64) Core ‘accelerator’, a Zynq-7000 Series Dual-core ARM A9 CPU/FPGA, 16GB RAM, Ethernet, HDMI, USB, running Linux…

Checkout the Adapteva Epiphany whitepaper

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Bluetooth 4 Low Energy Devices: iBeacon, Gecko


I am very excited by the capabilities (admittedly non-audio) that Bluetooth 4.0 Low Energy offers and some of the interesting product ideas that are popping up.

I just pledged to the Gecko indiegogo project  (after Steve Wozniak mentioned it) that wants to build smart-tags with sensors that notify your BT4 equipped phone (or other device) if they have been moved or removed from the 100′ range.

The iBeacon from startup estimate offers ‘micro-location based notifications’ to  both help map software work when indoors (no line of sight to GPS satelites) and provocatively, conversely to map user’s time and paths in a space. Impressively the iBeacon’s ARM Cortex M0 can run off a lithium cell while sending and receiving BT LE messages for up to two years (techie details & API).

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See you at Maker Faire 2013



makerfaireBay Area Maker Faire is this weekend: May 18th and 19th!

While it is melancholy not  to be rushing to polish details of a booth about now  (we were hoping to have something to demo using the exciting, progressing, but still non-available, Parallela $100 64-Core/FPGA ‘Supercomputer’) I am looking forward to visiting as civilian.

Please contact me if you would like to meet up at the fair!

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Getting Old: It is not an eye test!

I tried the Canadian Union Hearing Aid Center ‘Eye’ Test that has been circulating on the blogosphere.  Except it isn’t really an eye test at all:

They feel that people are more willing to have their eye sight tested than their hearing so they masquerade a hearing test as an eye test.

Am I getting old? I am disappointed I didn’t hear the embedded high frequency tone.

At first I blamed it on my laptop filtering the supposed noise. But then I ran the baudline spectrum analyzer using my laptop’s open mic. Sure enough there is a signal at 14250Hz (drat):

Untitled 20




Now I am blaming it on my cold!

But in case I am wrong read up on how age effects the upper range of the accepted human 20-20kHz hearing response via the wikipedia Fletcher-Munson Equal-loudness Curve article, and in more depth in Audio Anecdotes Volume 1.

Share your experience (and include the device used)!

Adendun: I can hear the tone on my iPhone especially with headphones but I do seem to be losing the frequency.  Maybe it is just the cold…


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Parallella: The $100 Kickstarter 64-Core/FPGA Supercomputer

Parallella Architecture

Parallella Architecture

A close friend just emailed me regarding Parallela, a “Worthy Kickstarter Project“. For a $100 contribution you receive (if they are successful) a Xilinx Zynq-7000 (Dual Core ARM + Programmable Logic) based single board computer with an Epiphany Multicore accelerator (16 or 64 core).

The Zynq-7000 contains a Dual-Core ARM Cortex-A9 with NEON vectorization, and a block of Xilinx Programmable Logic.

Depending on the chip selected Epiphany accelerator contains 16 or 64 RISC cores with over 32 GFLOP theoretical peak performance.

I am very excited by the possibilities enabled by combining a powerful mobile CPU with a block of programmable logic (with access to dev tools) and an array of parallel RISC cores to perform some serious Audio/Video Signal Processing, Cryptography, or other challenging application.

I am in for $100, and suggest you take a quick look since Funding ends Soon: Saturday October 27th!

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Finally ordered Raspberry Pi today

I received an emailed activation code for my Raspberry Pi pre-order today, the week AFTER Maker Faire. Sigh.  Actual fulfillment is another 5?! weeks out.  Consider this a head-start for next year!

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