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Physical Spectrum Analyser Answered

Hi!

I'm planning to build a physical Spectrum Analyser - a tangible model capable of showing audio levels (or something like that). A moving, undulating board of pillars that rise and fall with music.

Spectrum Analysers split audio inputs into 'Bands' and normally then express these values with light boards (LED's). I want to use an audio input to create kinetic power.

Is this possible?

I'm thinking a series/grid of actuators might serve to raise/lower blocks and columns.

This is all new to me! Much appreciated. Any thoughts?

Discussions

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Kiteman

3 years ago

It sounds like a cracking idea, but I'm afraid I don't know how - could the signal that drives the LEDs be put through an amplifier to drive a servo?

My personal favourite physical spectrum analyser if the Reubens tube, where flames show the sound waves.

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killerjackalopeKiteman

Reply 3 years ago

Missing the obvious! High power speaker drivers - specifically the driving piece with no cone attached have longer travel, that drops as you go up frequency.

However a block on top of different drivers, attached to the part the cone attaches to will both make some (not great) music and visualise the process.

For high frequencies there's not a lot to be done, they require very little travel to move that fast and even in very large (HF) horn units there's no visible effect as they move so fast.

These observations are based on PA's up to 15KW, the bass is easily seen, mids could be done but the high end is at best a blurring of the outlines at ear damaging volumes.

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Kitemankillerjackalope

Reply 3 years ago

I think what he's after is, effectively, a mechanical bar-graph - a physics rod that extends when a particular frequency is at a greater amplitude.

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JaminajarKiteman

Reply 3 years ago

I've been thinking. It doesn't matter if the higher frequencies oscillate too fast to see because I'm not wanting to visualise Hz (wavelengths) but Amplitude.

A Sparkfun Spectrum Shield can split a stereo audio input in to 7 'bands', the amplitude of these 7 frequencies can be visualised with LED's but I need to find a way of expressing it in mechanical power. To confirm what you've said above, I'm trying to make a 'mechanical bar-graph' of amplitude.

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KitemanJaminajar

Reply 3 years ago

I'm stepping into areas about which I am ignorant now, but could those 7 outputs each drive a servo? The arm of the servo could push a rod up and down - the servos etc could all be hidden inside a box, with your seven rods projecting out the top and moving up and down?

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JaminajarKiteman

Reply 3 years ago

That's exactly what I'm thinking! And to create the 'grid' (or an undulating board) I can repeat the 7 outputs. I'll keep you guys posted. Thanks again!

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KitemanJaminajar

Reply 3 years ago

Awesome - take lots of photos of the build, and video tests & the finished project.

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JaminajarKiteman

Reply 3 years ago

Kiteman - just watched a Pyro Board based on the Reubens tube idea. Check it out on: <https://www.youtube.com/watch?v=2awbKQ2DLRE> Thanks for the comment!

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killerjackalopeKiteman

Reply 3 years ago

As an addendum to my responses, I have just thought of a relatively complicated but off the shelf project to do this Reuben's tube style but physical might be a cool demonstration of pressure differentials too.

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Jaminajarkillerjackalope

Reply 3 years ago

Thanks for the information about frequency ranges - that's helpful. I've thrown some images in here so help explain my idea. A grid or, similar to what Kiteman describes as a 'bar-graph'.

The physical 'model' doesn't need to actually play music, just visualise it. Might there be a way of having a headphones 'out' (a Jack output).

Sorry to get you to repeat yourself - but are you saying that trying to visualise high frequencies would be pointless because they would move too fast for the human eye? (not a loaded question).

Audio Sculpture.jpgboxee-box-pandora.jpg