🔊 Sound Meter

A professional-grade sound level meter built with Flutter, providing real-time decibel monitoring, acoustic weighting filters, and recording capabilities — all from your phone's microphone.

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✨ Features

🎯 Real-Time Monitoring

• Live dB readings from the device microphone at ~30 FPS polling rate
• Radial gauge with animated needle powered by Syncfusion Flutter Gauges
• Min / Avg / Max tracking with exponential moving average (EMA) smoothing
• Environment classification — contextual labels like "Whisper", "Busy Traffic", "Thunder" based on current noise level

📊 Multi-View Charts

Cycle through three real-time visualization modes:

Chart	Description
Timeline	Rolling ~24-second dB history graph
Waveform	Raw PCM amplitude from the microphone membrane
FFT Spectrum	Logarithmic frequency spectrum (20 Hz – 20 kHz) with peak frequency annotation

🎛️ Acoustic Weighting Filters

Professional frequency and time weighting based on IEC 61672-1:2003:

• Frequency Weighting: A (dBA), C (dBC), Z (dBZ)
• Time Weighting: Fast (125 ms), Slow (1 s), Impulse (35 ms rise / 1.5 s decay)

🔧 Calibration

• Adjustable dB offset for hardware calibration against a known reference source

💾 Recording & History

• Save sessions with full metadata (min/max/avg dB, duration, dB history, weighting unit)
• Audio file recording (WAV) via native 32-bit float PCM capture
• Persistent history powered by hydrated_bloc — recordings survive app restarts
• Detail screen with stats card, area chart replay, and built-in audio playback (SoLoud)
• Rename, share, and delete recordings

🌗 Theme Support

• Light and dark mode with automatic system detection
• Manual toggle from the app bar
• Material 3 design system with a warm coral (#E85A3F) primary palette

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🏗️ Architecture

The app follows BLoC (Business Logic Component) architecture with a clean separation of concerns:

lib/
├── main.dart                    # App entry point, theme config, BLoC providers
├── blocs/
│   ├── sound_meter/             # Core audio state management
│   │   ├── sound_meter_bloc.dart
│   │   ├── sound_meter_event.dart
│   │   └── sound_meter_state.dart
│   ├── history/                 # Persistent recording history (HydratedBloc)
│   │   ├── history_bloc.dart
│   │   ├── history_event.dart
│   │   └── history_state.dart
│   └── theme/                   # Light/dark mode toggle
│       ├── theme_bloc.dart
│       ├── theme_event.dart
│       └── theme_state.dart
├── models/
│   └── recording_model.dart     # SoundRecording data model with serialization
├── screens/
│   ├── main_screen.dart         # Primary meter + charts UI
│   ├── history_screen.dart      # Saved recordings list
│   └── detail_screen.dart       # Recording detail + audio player
├── utils/
│   └── sound_utils.dart         # Frequency/time weighting math, dB references
└── widgets/
    ├── db_meter.dart            # Radial gauge + digital display
    ├── charts.dart              # Timeline, Waveform, FFT chart widgets
    ├── calibration_dialog.dart  # dB offset calibration UI
    ├── db_legend_dialog.dart    # dB reference table dialog
    └── weighting_dialog.dart    # Frequency/time weighting picker

Key Design Principles

• Utility-First Logic — All domain math (weighting filters, EMA calculations) lives in lib/utils/ as static, pure functions for easy unit testing
• Semantic Theming — All colors are resolved via Theme.of(context).colorScheme; no hardcoded color constants in widgets
• Reactive State — BLoC pattern with flutter_bloc for predictable, testable state transitions

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🛠️ Tech Stack

Category	Package	Purpose
State Management	flutter_bloc / hydrated_bloc	Reactive BLoC pattern with persistence
Audio Capture	flutter_recorder	Native microphone access (PCM / WAV)
Audio Playback	flutter_soloud	Low-latency audio playback engine
Signal Processing	fftea	Fast Fourier Transform for spectrum analysis
Gauges	syncfusion_flutter_gauges	Radial gauge visualization
Charts	syncfusion_flutter_charts	Timeline, waveform, and FFT charts
Permissions	permission_handler	Runtime microphone permission
File System	path_provider / path	App documents directory management
Formatting	intl	Date/time formatting
Sharing	share_plus	Share recordings externally
IDs	uuid	Unique recording identifiers

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🚀 Getting Started

Prerequisites

• Flutter SDK >= 3.11.1
• Android SDK (API 21+)
• A physical device with a microphone (emulators have limited audio support)

Installation

# Clone the repository
git clone https://github.com/agnivon/sound_meter.git
cd sound_meter

# Install dependencies
flutter pub get

# Run on a connected device
flutter run

Building for Release

# Android APKs (split by ABI for smaller downloads)
flutter build apk --split-per-abi

# Android App Bundle
flutter build appbundle

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🧪 Testing

The project includes a comprehensive test suite covering unit, BLoC, and widget tests:

# Run all tests
flutter test

# Run with coverage
flutter test --coverage

Test Structure

test/
├── blocs/
│   ├── history_bloc_test.dart
│   ├── sound_meter_bloc_test.dart
│   └── theme_bloc_test.dart
├── screens/
│   ├── detail_screen_test.dart
│   ├── history_screen_test.dart
│   └── main_screen_test.dart
├── utils/
│   └── sound_utils_test.dart
└── widgets/
    ├── calibration_dialog_test.dart
    ├── db_meter_test.dart
    └── weighting_dialog_test.dart

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📋 Permissions

| RECORD_AUDIO | Android | Microphone access for sound measurement |

The app requests microphone permission at startup. All audio processing is performed on-device — no data is transmitted externally.

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📄 License

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

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🙏 Acknowledgements

• Syncfusion for their excellent Flutter gauge and chart libraries
• flutter_recorder for native audio capture
• SoLoud for high-performance audio playback
• IEC 61672-1:2003 standard for acoustic weighting filter formulae