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By prodestrian
This was sparked by a question posted in the Arduino for Ghostbusters Props Facebook group, but I thought it might be interesting to some people here.

I was able to reverse engineer and digitally recreate the post-capture beeps of the 84 trap by analyzing the audio from the Sedgewick ballroom scene (actually from the cleaned up versions by ryusui which were shared in Ectolabs' trap build thread).

We all know it's four descending tones during the bargraph activation:

These tones appear to be:
1323Hz => 663Hz => 329Hz => 168Hz

Followed by 1015Hz beeps lasting ~55ms with a ~260ms delay between them.

It was trivially easy to replicate this using Audacity by generating Sinewave tones at those frequencies, here's my lazy attempt (Yes I know the beeps aren't evenly spaced, I was copy/paste/dragging them by hand):

The significance of this isn't that I can create better WAV/MP3 files than what ryusui shared, those files already sound super clear and I'd recommend those to most people. It's more that it's potentially possible for someone to generate the sounds in real-time as part of their build, so they don't need to use a separate soundboard unless they also want to have the opening/closing/sparking sounds from the film. This could save a lot of space/cost, especially if you just want a static trap with flashing lights and some beeping sounds. It would also save a lot of battery power, and keep the beeping sound in sync with the blinking red lamp (you could have it beeping/flashing all day at a convention).

The only problem is I'm not sure how to generate sinewave tones using an Arduino, or if there's some other setup which can be used. There are some libraries for doing this but they seem pretty rough and inefficient. And the Arduino "tone()" functions all output squarewave tones, which sound terrible.
I believe my Teensy Audio Shield can generate sinewave tones, but that's not a cheap device, and at that point you may as well just use the movie sounds anyway. It might be possible to use some kind of small i2c DAC but this is something I don't have a lot of experience with.

There's also other methods but most of these go over my head: ... -sine-wave

Anyway, just putting this out there in case it helps someone else in the future. If anyone does manage to generate the tones using an Arduino or some analog components please let me know!

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