WAV Trigger: One Sound FX card to rule them all

April 21, 2015

Max The Magnificent-April 21, 2015

My dreams have been answered. I am currently performing my happiest of happy dances (it's not a pretty sight). Let me explain. For the longest time, I've been looking for a sound effects card to use in my hobby projects. In the case of my Inamorata Prognostication Engine, for example, the front panel is festooned with antique push-buttons and toggle switches and knobs and dials. When I flick a switch on this little beauty, I don’t want to be disappointed with a sheepish "click" that sounds embarrassed to be making itself heard. My ears deserve to be caressed by a satisfying "ker-thump," followed by the sounds of clockwork contrivances and mechanical mechanisms and balls rolling down chutes and suchlike.

Sad to relate, I couldn’t find anything to fit the bill. For some applications synthesized sound might be the way to go, such as the effects one can obtain using a GinSing Shield, for example.

In the case of my projects, however, I want to use real-world sound samples, so next I looked at traditional audio shields such as the WAVE Shield from Adafruit.

The WAVE Shield is described as being ideal for adding audio effects to one's projects. The problem is that -- like the vast majority of cards of this ilk -- it can only play a single audio file at a time. For my projects, by comparison, I want to be able to add "layers of sound" corresponding to different actions taking place.

Eventually, a group of us started to consider designing and building our own card, as discussed in Sound Effects Shield for Arduino: The Specification. This project has been shuffling along in the background, but everyone is busy and nothing really substantial has emerged.

And then, just a couple of days ago, my chum Duane Benson sent me an email saying:

I've been busy getting ready for Maker Faire and haven't had time to work on our sound player, but this sound effects board may be what we're looking for.

"This" turned out to be the WAV Trigger board, which is supplied by our friends at SparkFun, but which was actually created by my new hero Jamie Robertson, who is a senior Disney Imagineer by day and a mad scientist designer by night (check out Jamie's website).

OMG! As I said at the beginning of this column, the WAV Trigger board is the answer to my dreams. The key feature is that it's Polyphonic, which means "many-voiced" or "capable of producing many sounds simultaneously." In fact, the WAV Trigger can play and blend up to 14 stereo audio streams at the same time, where each stream can be started, paused, resumed, or terminated independently. The board also automatically performs voice stealing, which means that -- if it's told to play a new audio stream while it is currently playing the maximum number of streams -- it will automatically drop the oldest audio stream and add the latest request to the mix.

The way this works is that you use an audio editor like Audacity to prepare your sound snippets on your host computing platform (Windows, Linux, etc.). You can use your own sound bites and/or you can download them from loads of websites. Then you copy these sound files onto a Micro-SD card, which you plug into the WAV Trigger board.

The board I have supports up to 1,000 uncompressed 16-bit, 44.1kHz stereo WAV files (CD-quality), which is way more than I personally need, especially remembering that I only require short sound snippets and an 8GB Micro-SD card can hold over 12 hours of stereo WAV audio. (I was chatting with Jamie on the phone earlier, and he is currently working on a new version of the firmware that will support up to 2048 tracks.)

The simplest way to use the WAV Trigger is by means of its 16 trigger inputs, which can be set to be edge or level sensitive, and which can be controlled by simple switches or by a microcontroller. In this case, activating a trigger input will cause a corresponding audio file to be added into the mix (the trigger-to-sound delay is typically only 8 milliseconds). Alternatively, you can control the WAV Trigger using a simple serial protocol -- an Arduino Library is available to make this easy -- that allows you to access all 1,000 sound files. But instead of my waffling on, check out This Video and tell me what you think.

I can’t help myself. I'm currently chuckling and chortling with delight. My WAV Trigger is sitting here on my desk looking up at me with a "hello handsome, are you ready for some fun" look (metaphorically speaking). What can I say? Yes, I am indeed ready for some fun. Watch this space for future updates as I integrate WAV Triggers into all of my projects.

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