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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Sitting out Maker Faire 2012


Regretfully it seems as if AudioAnecdotes won’t have a booth at Maker Faire this year.  We had planned fun audio (and even ultra-sonic!) projects involving the hot but unobtainable Raspberry Pi but alas Maker Faire registration has come and gone and we have yet to even receive a ship date on our boards.

Disappointing but will be fun to wander the Faire as a civilian-maker for a change.

Please be sure to contact us if you are planning on attending and want to hook up while in the Bay Area.

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DigiPen to offer Degrees in Sound Design and Engineering

DigiPen Institute of Technology

DigiPen will be offering two new degrees in Sound Design for Fall 2012. A Bachelor of Arts in Music and Sound Design, and a Bachelor of Science in Engineering and Sound Design. It sounds as if they have some great people associated with the program “Dr. Richard Karpen, Director of the University of Washington’s School of Music, Guy Whitmore, Audio Director at PopCap Games, Inc., and Martin O’Donnell, Audio Lead at Bungie“.

However I still wonder if they will use my classes or books (it has been a long time since I left Redmond for Cupertino).  I really miss teaching my Audio Synthesis and Data Compression classes at DigiPen.  I had a wonderful experience with the talented students.

These new programs should improve the already rich curriculum.

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