Spectrogram
The Spectrogram extends the Spectrum into the time dimension. Where a spectrum shows the frequency content of a single moment, a spectrogram shows how that frequency content evolves over time. You can think of a spectrogram as many spectra placed side by side and viewed from above.
From Spectrum to Spectrogram
The two views differ in which axes they use:
| Spectrum | Spectrogram | |
|---|---|---|
Horizontal axis |
Frequency |
Time |
Vertical axis |
Intensity |
Frequency |
Intensity shown as |
Height of the curve |
Colour (or brightness) |
Time shown as |
(none — single instant) |
Horizontal position |
The spectrogram trades the spectrum’s intensity axis for a time axis, and represents intensity through colour instead. Brighter or more saturated colours indicate stronger frequency components; darker colours, weaker ones.
Reading the Display
What you see on a spectrogram lines up with a small vocabulary of patterns:
-
a bright horizontal line — a frequency that is sustained over time (a held tone);
-
several parallel horizontal lines — the harmonics of a musical tone, evenly spaced on a linear scale and progressively closer on a logarithmic one;
-
vertical bright stripes — moments where many frequencies sound at once, such as a percussive attack or an unvoiced consonant;
-
gently wavy harmonics — vibrato, the periodic modulation of pitch;
-
moving formant bands — bright zones that drift across several harmonics, typical of a vowel transition;
-
dark areas — frequencies with little or no energy at that moment.
Why the Spectrogram Is Powerful for Singing
Consider a singer holding one note and then changing to another:
-
On the spectrum, the peaks suddenly jump to new positions, and the previous note is gone.
-
On the spectrogram, the harmonics of the first note appear as horizontal lines, then move to the new positions of the second note’s harmonics. The transition between the two is preserved.
This is what makes the spectrogram the central display for singing analysis: it shows not only the notes themselves, but the way the singer moves between them — register transitions, vibrato, vowel changes, and shifts in vocal timbre.
In VoceVista
The Spectrogram is part of the Analyzer View. The frequency scale, FFT size, time resolution, and colour mapping all affect what shows up in the display; see Analyzer Settings and the Colormap Editor. For the upper limit of detail the spectrogram can show, including the analyzer’s resolution and refresh-rate ceiling, see the high-resolution audio spectrum analyzer page.