Spectrograms

A visual representation of the spectrum of frequencies in a signal as it varies with time.

Spectrograms map sound onto a three-dimensional landscape: time sits on the horizontal axis, frequency (Hz) on the vertical, and amplitude (dB) is represented by color intensity. Engineers use them to isolate specific transients in complex audio files, such as a 2kHz whistle in a field recording or a 60Hz hum in a studio track. By converting raw waveforms into heat maps, tools like iZotope RX or Audacity allow users to identify patterns invisible to the naked ear (like the harmonic structures of a Stradivarius violin or the ultrasonic clicks of a bat). This visual data is the backbone of modern speech recognition, sonar analysis, and bioacoustics research.

https://pudding.cool/2018/03/spectrogram/