About This Tool
This interactive spectrogram generator is a powerful educational tool designed for students,
educators, and professionals in fields like signal processing, biomedical engineering,
communications, and audio analysis. It provides a hands-on environment to explore how different
signals appear in the frequency domain over time, all rendered synthetically and in real-time
within your browser. By manipulating signal parameters and observing the immediate visual and
auditory feedback, users can build a strong intuition for complex signal processing concepts.
Understanding the Spectrogram
A spectrogram is a visual representation of a signal's frequency content as it changes with time.
Here’s how to read the display:
- X-Axis (Time): This horizontal axis represents the passage of time, from
left to right, corresponding to the selected `Time Window`.
- Y-Axis (Frequency): This vertical axis represents frequency, measured in
Hertz (Hz). Lower frequencies are at the bottom, and higher frequencies are at the top, up
to the selected `Max Frequency`. You can switch between a linear and logarithmic scale,
which is often better for viewing biomedical signals or audio.
- Color (Intensity/Power): The color of any point on the graph indicates the
power, or "loudness," of the signal at that specific frequency and time. The color map
(e.g., Viridis, Grayscale) translates power levels into different hues. Brighter or "hotter"
colors signify a stronger signal component.
Signal Explanations
Each signal type has unique characteristics and real-world applications:
- Sine Wave: The fundamental building block of all signals. It represents a
single, pure frequency.
- Chirp Signal: A signal in which the frequency changes over time. Widely
used in radar, sonar, and for testing the frequency response of systems.
- Pulse Train: A series of repeating on/off pulses. It's fundamental to
digital communications, representing binary data streams.
- White Noise: A random signal containing equal intensity at all frequencies,
often used to model background noise or to test system robustness.
- EEG (Electroencephalogram): Measures electrical activity in the brain. The
distinct frequency bands (Delta, Theta, Alpha, Beta) are associated with different mental
states like deep sleep, relaxation, and active thinking.
- ECG (Electrocardiogram): Records the heart's electrical rhythm, showing
distinct features like the P-wave, QRS complex, and T-wave that correspond to different
phases of a heartbeat.
- EMG (Electromyogram): Captures the electrical signals produced by muscle
activity. The signal's amplitude and frequency increase with the level of muscle
contraction.
- EOG (Electrooculogram): Detects electrical potential changes from eye
movements, useful in sleep studies to identify REM sleep stages.
- PPG (Photoplethysmogram): Measures changes in blood volume in the
microvascular bed of tissue, commonly used by smartwatches and pulse oximeters to determine
heart rate.
Future Directions
This application is actively being improved. Potential future enhancements include:
- Signal Mixing: An interface to additively combine multiple signal types to
observe constructive and destructive interference.
- Real-time Microphone Input: Functionality to process and visualize audio
directly from a user's microphone in real-time.
- Advanced STFT Controls: Expose Short-Time Fourier Transform parameters,
allowing users to change the FFT size, window overlap, and apply different windowing
functions (e.g., Hann, Hamming, Blackman).
- Data Export: Add features to export the spectrogram as a high-resolution
image (PNG) or the raw signal data as a CSV or WAV file for external analysis.