Long-Term Average Spectrum

A single Spectrum captures one moment of a recording; an averaged Spectrum captures a short window. The Long-Term Average Spectrum (LTAS) goes further: it averages spectra over an extended section of the recording — often the whole file or a long marked region — to reveal the overall spectral fingerprint of a voice or instrument.

Why Average Over a Long Range?

When the analysis window is short, the spectrum changes constantly: each new pitch, vowel, or breath rearranges the picture. A long-term average smooths through these short-term changes and leaves what stays roughly constant across the recording — the typical balance between low and high frequencies, the prominence (or absence) of the singer’s formant, the overall noisiness of the voice.

This makes the LTAS the right tool whenever the question is about style, identity, or training, rather than about a specific note:

  • a stable, settled spectral picture, less affected by the particular notes being sung;

  • a clearer view of resonance features that persist throughout the recording — for example, the singer’s formant cluster around 2.5–3.5 kHz in trained classical voices;

  • a useful basis for comparison: between two sections of the same recording, between two recordings of the same singer, or between two different singers.

What the LTAS Does Not Show

The LTAS averages intensities across time, so it discards everything about when something happened. A passage with strong vibrato, a sudden register change, or a pitched ornament all dissolve into the same long-term picture. For those phenomena, the Spectrogram remains the right tool. The LTAS and the Spectrogram are complements: the spectrogram shows what changes, the LTAS shows what stays.

Choosing the Section to Average

The averaging only makes sense over material that is reasonably uniform. Averaging across silence inflates the noise floor; averaging across very different material — loud and quiet, sung and spoken, two different vowels — blurs together styles that are worth keeping separate. A typical workflow is to mark a passage of comparable material with a Range Marker and compute the LTAS only over that marker.

In VoceVista

The Long-Term Average Spectrum is part of VoceVista Pro. It is computed over the current selection or over a marker; see Long-Term Average Spectrum for the operational details. To compare LTAS curves between markers, see also Markers. The smoothed-curve overlay (see Smoothed Curves and the Spectral Envelope) is often used together with the LTAS to highlight the formant envelope.