Questions, answered
How is a spectrogram different from a waveform?
A waveform shows loudness over time only. A spectrogram breaks each moment into its frequency content, so you can see hum, hiss, and which parts of the spectrum carry the sound.
How do I spot background hum?
Look for a constant horizontal line near the bottom at 50 or 60 Hz, often with fainter lines at multiples above it. A narrow filter at that frequency removes it with minimal effect on the rest.
What is the sharp cutoff near the top of my spectrogram?
That is a lossy codec’s bandwidth limit, typically between 15 and 16 kHz. It means the audio was encoded as MP3 or AAC at some point, regardless of the file’s current format.
Should I use a linear or logarithmic frequency scale?
Logarithmic for speech and music, because it matches how we hear and gives the low end the space it deserves. Linear is useful when you are hunting a specific high-frequency tone.
Can I make a spectrogram from a video?
Yes — the video’s soundtrack is analysed directly, so there is no need to extract the audio first.
