🎵 Sound Chat - Text Messages via Sound Waves

A Python project that enables two devices to exchange text messages using sound waves. Perfect for hackathons, demos, and exploring digital signal processing!

🚀 Quick Start

1. Setup Virtual Environment

# Create virtual environment
python -m venv sound-chat-env

# Activate virtual environment
sound-chat-env\Scripts\Activate.ps1

# If you get execution policy errors, run this first:
Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser

2. Install Dependencies

# Install all required packages
pip install -r requirements.txt

3. Test the System

On Device 1 (Sender):

# Send "HELLO" message
python sender.py "HELLO"

On Device 2 (Receiver):

# Start listening for messages
python receiver.py

📁 Project Structure

sound-chat/
├── sender.py          # Transmits text as sound waves
├── receiver.py        # Receives and decodes sound waves
├── requirements.txt   # Python dependencies
└── README.md         # This file

🔧 How It Works

Technology: FSK (Frequency Shift Keying)

• Bit '0': 1000 Hz tone
• Bit '1': 2000 Hz tone
• Start Signal: 500 Hz tone
• End Signal: 3000 Hz tone

Process

1. Sender: Text → Binary → Audio frequencies → Sound waves
2. Receiver: Sound waves → Frequency analysis → Binary → Text

📋 Detailed Usage

Sender Options

# Basic usage
python sender.py "YOUR MESSAGE"

# Custom parameters
python sender.py "HELLO WORLD" --sample-rate 44100 --bit-duration 0.1

Parameters:

• message: Text to send (required)
• --sample-rate: Audio sample rate (default: 44100 Hz)
• --bit-duration: Duration per bit in seconds (default: 0.1s)

Receiver Options

# Basic usage
python receiver.py

# Custom parameters
python receiver.py --timeout 60 --sample-rate 44100 --bit-duration 0.1

Parameters:

• --timeout: Recording timeout in seconds (default: 30s)
• --sample-rate: Audio sample rate (default: 44100 Hz)
• --bit-duration: Duration per bit in seconds (default: 0.1s)

🎤 Hardware Setup

For Same Computer Testing

1. Use different audio devices (if available)
2. Use headphones + microphone to prevent feedback
3. Adjust volume to medium level

For Different Computers

1. Position devices close (1-3 feet apart)
2. Use external speakers for better transmission
3. Minimize background noise

🛠️ Troubleshooting

Common Issues

1. Permission Errors

PermissionError: [Errno 13] Permission denied

Solution:

Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser

2. Microphone/Speaker Not Working

OSError: No Default Input Device Available

Solutions:

• Check Windows audio settings
• Grant microphone permissions to Python
• Test with python -c "import sounddevice; print(sounddevice.query_devices())"

3. PyAudio Installation Issues

ERROR: Microsoft Visual C++ 14.0 is required

Solutions:

# Option 1: Install pre-compiled wheel
pip install pipwin
pipwin install pyaudio

# Option 2: Use conda instead
conda install pyaudio

4. No Message Received

Check:

• Volume levels (not too low/high)
• Background noise
• Distance between devices
• Both devices using same parameters

5. Partial/Corrupted Messages

Solutions:

• Increase bit duration: --bit-duration 0.2
• Reduce background noise
• Move devices closer
• Check audio device quality

Audio Device Testing

# Test audio devices
python -c "import sounddevice as sd; print(sd.query_devices()); sd.check_input_settings()"

# Test microphone
python -c "import sounddevice as sd; import numpy as np; print('Recording...'); data = sd.rec(2*44100, samplerate=44100, channels=1); sd.wait(); print(f'Max level: {np.max(np.abs(data))}')"

🎯 Demo Tips

For Hackathon Presentations

1. Test everything beforehand

   # Quick test sequence
   python sender.py "TEST" &
   timeout 5
   python receiver.py --timeout 10

2. Prepare backup messages

   # Create test script
   echo 'python sender.py "HELLO HACKATHON"' > test.bat

3. Use reliable hardware

   • External USB microphone/speakers
   • Wired connections when possible

4. Have multiple test messages ready

   python sender.py "DEMO"
   python sender.py "HELLO WORLD"
   python sender.py "SOUND CHAT WORKS"

Performance Optimization

# Faster transmission (shorter messages)
python sender.py "HI" --bit-duration 0.05

# More reliable transmission (longer messages)
python sender.py "HELLO" --bit-duration 0.2

🔍 Advanced Usage

Custom Frequency Settings

Modify the frequency constants in both files:

# In sender.py and receiver.py
self.freq_0 = 1000      # Frequency for bit '0'
self.freq_1 = 2000      # Frequency for bit '1'
self.freq_start = 500   # Start signal
self.freq_end = 3000    # End signal

Multiple Device Communication

# Device 1 → Device 2
python sender.py "MSG1"

# Device 2 → Device 1  
python sender.py "MSG2"

# Device 3 listening
python receiver.py

📊 Technical Specifications

• Frequency Range: 500-3000 Hz
• Data Rate: ~80 bits/second (default settings)
• Character Encoding: ASCII (8 bits per character)
• Sample Rate: 44.1 kHz
• Transmission Range: 1-10 meters (depending on environment)

🚨 Limitations

1. Noise Sensitivity: Background noise can interfere
2. Range Limited: Works best within a few meters
3. ASCII Only: Non-ASCII characters may not transmit correctly
4. One-Way: No built-in acknowledgment system

🔬 Extending the Project

Ideas for Enhancement

1. Error Correction: Add checksums or parity bits
2. Compression: Implement text compression
3. GUI Interface: Create a user-friendly interface
4. File Transfer: Extend to send small files
5. Two-Way Chat: Implement full duplex communication

🆘 Getting Help

If something doesn't work:

1. Check this README for common solutions
2. Test each component separately:

   python -c "import numpy, scipy, sounddevice; print('All imports work!')"

3. Verify audio hardware:

   python -c "import sounddevice as sd; sd.default.device = [0, 1]; print(sd.query_devices())"

Contact Information

For hackathon support or questions, check the project repository or ask your mentors!

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Happy Hacking! 🎉

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