Spectrum is a room frequency response app designed to be easy to use while packing the features that are useful for audio and HiFi enthusiasts. While it isn't going to replace an ECM8000, it is at least portable, free and can double as a sound meter.
To download spectrum, head to the releases tab and download the APK. Or, click on the button below. Coming soon to F-droid.
- jjoe64 for GraphView library - https://github.com/jjoe64/GraphView/
- lucns for their FFT algorithm - https://github.com/lucns/Android-Audio-Sample
- Android Developer Documentation
- Stack Overflow ;)