Audacity

Audacity is the de facto standard for EVP (Electronic Voice Phenomena) analysis in paranormal investigation. Its spectrogram view can reveal frequency components invisible to the ear — anomalous voices and sounds often appear as distinct spectral signatures between 300Hz and 3kHz when the recording appears silent on playback. Investigators routinely apply Audacity's built-in noise reduction to subtract ambient environmental noise (HVAC, traffic, investigator movement) before listening for residual anomalies.

The spectrogram display is particularly powerful: set FFT size to 1024 or 2048 for EVP work, choose a logarithmic frequency scale, and use high-contrast colouring. Anything that shouldn't be there — a syllable, a partial word, a tonal event — will stand out visually against the noise floor even before you hear it. Combine this with Audacity's ability to slow audio to 50% speed without pitch shift (Change Tempo effect) to catch fast, clipped EVP responses.

For overnight continuous recordings, use Audacity's built-in Silence Finder (Analyse menu) to automatically scan hours of audio and create labels at every non-silent event above a set threshold. This compresses a 6-hour silent session into a list of 40 events to review in 20 minutes. Export labels as a text file to build an evidence timeline.