Oscilloscopes are incredibly useful for visualizing signals (audio or otherwise), but unless the software you’re using already has one built in, it’s not necessarily easy to see what’s going on.
- First you’ll need a tool to route audio internally. I used Soundflower, a free kernel extension originally developed by Cycling ’74 (the company that makes Max/MSP). Update: Go here to download the newest version with updated instructions. After installing (you may need to reboot), all audio apps will show Soundflower as a system input or output. Soundflower offers a 2-channel and a 64-channel bus; you’ll likely usually only need the 2-channel bus.
- Set your audio source to output to Soundflower. In the above video, I’m using Puredata, so I go to Media > Audio Settings… and set Output Device 1 to Soundflower (2ch). (Make sure you’ve enabled DSP if you’re also using Pd!)
- Now you need an oscilloscope. I’m using iSpectrum, a free OS X app that also has a great spectrum analyzer/waterfall, which gives you a realtime color graph of your spectrum over time. Set the input to Soundflower (2ch) and you should immediately see your signal.
- If you want to hear your audio on your speakers as well, iSpectrum has a handy “Play Through” option on the Waterfall view.
- That’s it!