Spectrogram Text Art

Synthesise audio that displays readable text when viewed as a spectrogram.

The function rasterises text with a built-in 5 × 7 bitmap font. Each bitmap column becomes a time slice; each “on” pixel becomes a sine wave at the corresponding frequency between freq_lo and freq_hi. A 3 ms raised-cosine crossfade suppresses clicks at column boundaries. The output is normalised to 0.9 peak amplitude.

pyminidsp.spectrogram_text(text, freq_lo=200.0, freq_hi=7500.0, duration_sec=2.0, sample_rate=16000.0)[source]

Synthesise audio that displays readable text in a spectrogram.

Parameters:

  • text – ASCII string to render.

  • freq_lo – Lowest frequency in Hz.

  • freq_hi – Highest frequency in Hz.

  • duration_sec – Total duration in seconds.

  • sample_rate – Sample rate in Hz.

  • text – Printable ASCII string to render (must be non-empty).

  • freq_lo – Lowest frequency in Hz (bottom of text).

  • freq_hi – Highest frequency in Hz (top of text, must be < Nyquist).

  • duration_sec – Total duration in seconds.

  • sample_rate – Sample rate in Hz.

Returns:

numpy array of audio samples.

Returns:

Array of audio samples.

sig = md.spectrogram_text("HELLO", freq_lo=200.0, freq_hi=7500.0,
                           duration_sec=2.0, sample_rate=16000.0)
# View the spectrogram of sig to see "HELLO" spelled out