librosax.feature.spectral_centroid

spectral_centroid(*, y: Array | None = None, sr: float = 22050, S: Array | None = None, n_fft: int = 2048, hop_length: int = 512, freq: Array | None = None, win_length: int | None = None, window: str = 'hann', center: bool = True, pad_mode: str = 'constant') → Array

Compute the spectral centroid.

Each frame of a magnitude spectrogram is normalized and treated as a distribution over frequency bins, from which the mean (centroid) is extracted per frame.

More precisely, the centroid at frame t is defined as:

centroid[t] = sum_k S[k, t] * freq[k] / (sum_j S[j, t])

where S is a magnitude spectrogram, and freq is the array of frequencies (e.g., FFT frequencies in Hz) of the rows of S.

Users should ensure S is real-valued and non-negative.

Parameters:

• y –

  Audio time series. The last axis must be time.

  • (T,) - single waveform

  • (B, T) - batch of waveforms

• sr – Audio sampling rate

• S – (optional) Pre-computed spectrogram magnitude with shape (..., F, N)

• n_fft – FFT window size

• hop_length – Hop length for STFT

• freq – Center frequencies for spectrogram bins. If None, FFT bin center frequencies are used.

• win_length – Window length

• window – Window function

• center – If True, pad the signal

• pad_mode – Padding mode

Returns:

Spectral centroid frequencies with shape (..., 1, N) where N is the number of frames. The frequency axis is reduced to size 1.

• (T,) → (1, N)

• (B, T) → (B, 1, N)