The famous chirp is grounded in detector strain, but published audio may be
filtered, amplified or shifted. We compare time-domain strain, a spectrogram
and playback while naming each operation.
Interferometer strain → calibrate and band-pass → isolate a short event window
→ optionally shift or amplify → render to audio. The rising frequency is in
the signal; the playback level and audible placement are presentation choices.
Use this page before the slides, then return to the checkpoint after the lab.
After this week, you can
Identify strain, sampling rate and detector as parts of a GWOSC record.
Separate filtering and amplification from the event's rising frequency.
Compare two detectors before accepting a polished combined rendering.
Inspectable teaching model
relative envelope
0.050.080.130.210.360.580.900.20
A schematic event envelope for comparing operations, not released strain data. Values are a teaching model, not an astronomical observation.
Worked notebook
A processing ladder for GW150914
A schematic event envelope for comparing operations, not released strain data.
Begin with the same short event window for both detectors.
Compare raw context, band-passed data and an amplified rendering.
State any speed or frequency shift independently from filtering.
Use spectrograms to check whether audible clarity came from the event or the operation.
What the method supportsThe rising time-frequency pattern supports the chirp description. Loudness, noise suppression and placement inside the audible range belong to the rendering.
CheckpointA filtered version is easier to hear than the surrounding strain. Does that make it stronger detection evidence?Reveal the reasoning
No. Audibility and detection confidence answer different questions.
Filtering can expose a known pattern to human hearing, but detection uses calibrated data, detector agreement and statistical analysis. A clearer playback does not add independent evidence.