Spectrogram was PocketChirp’s audio-visualization app, linked by the original article at this October 23, 2008 URL to pocketchirp.com/spectrogram. The historical download link identifies Apple app ID 293980373. It used microphone input to display frequency content in a scrolling graph, making a normally invisible aspect of sound visible on the phone.
Frequency over time
The original description advertised built-in or external microphone input, adjustable sensitivity, linear and logarithmic frequency scales, and an analysis range extending to 20 kHz. Those are historical specifications supplied by the listing, not measurements we have reproduced or a guarantee about an old phone’s microphone response.
The Audacity manual provides useful background on the visualization: a spectrogram represents changes in energy across frequency bands over time. It can reveal the onset of a sound and patterns that are less obvious in a conventional waveform. That explains the type of display; it does not establish that PocketChirp implemented Audacity’s controls or processing options.
Ask one question of the display
For a learning exercise, compare a sustained sound with a short tap and observe which pattern lasts and which appears briefly. Keep the source and microphone position consistent while comparing them. This is a proposed way to explore a working sound visualizer, not a reported experiment conducted in the legacy app.
Record the scale and sensitivity settings with any screenshot. A change in display settings can change the apparent pattern, so two colorful images are not automatically comparable measurements. A phone display alone should not be treated as a calibrated instrument for an equipment specification or an exposure assessment.
Keep the original product distinct
The title Spectrogram describes a visualization as well as this particular app. The PocketChirp link and numeric ID are therefore essential when locating historical material. Current availability and microphone compatibility remain unverified, and no audio test was performed for this newly written overview. Browse our music and reference-app archive for related histories.