Android Audio Spectrograph

A real-time audio spectrum analyzer for Android that provides both traditional FFT and waterfall display modes. This application visualizes audio input from your device's microphone as a frequency spectrum, useful for audio analysis, music visualization, and educational purposes.

Features

• Real-time audio spectrum analysis
• Two visualization modes:
  • Traditional FFT bar graph display
  • Waterfall spectrogram display
• Adjustable frequency range selection
• Multiple color schemes:
  • Blue to Red (classic spectrum)
  • Black to Purple to Red
• Smooth, efficient rendering optimized for Android
• Configurable display parameters

Screenshots

From left to right, the screenshots show

1. Regular FFT mode using blue to red color scheme
2. Regular FFT mode using black to red color scheme
3. Waterfall FFT mode, both color schemes shown
4. Gain adjustment setting, range of 1.0 to 11.0

Requirements

• Android Studio Arctic Fox or newer
• Android SDK 21 or higher (Android 5.0+)
• Device with microphone support
• Android device with RECORD_AUDIO permission

Installation

1. Clone this repository:

git clone https://github.com/ctracy/AudioSpectrograph.git

2. Open the project in Android Studio
3. Sync project with Gradle files
4. Build and run on your Android device

Usage

1. Launch the app
2. Grant microphone permissions when prompted
3. The app will begin displaying the audio spectrum immediately
4. Use the interface buttons to:
   • Toggle between FFT and Waterfall modes
   • Adjust the frequency range
   • Change color schemes

Controls

• Toggle Button: Switch between FFT and Waterfall display modes
• Frequency Range: Adjust the visible frequency spectrum
• Color Scheme: Toggle between different visualization color patterns

Technical Details

• Uses Android's AudioRecord API for audio capture
• Implements Fast Fourier Transform (FFT) for frequency analysis
• Custom View implementation for efficient rendering
• Supports both regular and waterfall spectrograms
• Thread-safe audio processing and visualization

Permissions

The app requires the following permission:

<uses-permission android:name="android.permission.RECORD_AUDIO" />

Building from Source

1. Open the project in Android Studio
2. Ensure all dependencies are properly synced
3. Build the project (Build → Make Project)
4. Run on an Android device or emulator

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the MIT License - see the LICENSE file for details

Acknowledgments

• The FFT implementation in AudioProcessor uses JTransforms, a multithreaded FFT library
• The specific implementation uses a 1D FFT on float data (FloatFFT_1D)
• Inspired by traditional audio analysis tools
• Built with Android Studio and Kotlin/Java

Known Issues

• Sometimes the display doesn't start correctly on the first load, try re-running until fixed
• Gain is more like a "contrast" control than a true amplitude gain
• Not a "true" gain in the signal processing sense since it is being applied after normalization

Future Enhancements

• Additional color schemes
• Save/export capabilities
• More visualization modes
• Frequency labeling
• Audio file input support

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Note: This application is designed for educational and analytical purposes. The accuracy of the frequency analysis depends on the quality of the device's microphone and sampling capabilities.