Audio manipulation ranges from simple cuts and splices to sophisticated frequency-domain editing. This module teaches you to detect the artifacts that audio editing tools leave behind.
Common Manipulation Types
Temporal Edits
Cuts, insertions, deletions, and rearrangements. Detectable through background noise discontinuities, electrical network frequency (ENF) breaks, and crossfade artifacts.
Spectral Edits
Frequency-selective modifications — noise reduction, equalization, pitch shifting. Visible as unnatural spectral boundaries in spectrogram analysis.
Electrical Network Frequency (ENF) Analysis
Any audio recorded near electrical infrastructure captures a faint hum at the local power grid frequency (50Hz or 60Hz). This frequency fluctuates slightly over time in a pattern unique to each moment. ENF analysis can verify when a recording was made and detect temporal edits — a splice creates a discontinuity in the ENF trace.
Background Noise Analysis
The noise floor of a recording — ambient sound, microphone self-noise, room tone — should be consistent throughout an authentic recording. Edits introduce mismatches in noise characteristics that are invisible to casual listening but clearly visible in spectral analysis.
| Artifact | Indicates | Detection Method |
|---|---|---|
| Noise floor discontinuity | Splice or insertion | Spectrogram visual inspection |
| ENF break | Temporal edit or fabrication | ENF extraction and matching |
| Phase discontinuity | Poor crossfade at edit point | Waveform zero-crossing analysis |
| Double compression | Re-encoded after editing | Compression artifact analysis |
Audio manipulation detection builds on Audio Fundamentals and the spectral analysis skills from earlier modules.