Left: 2D wavelet transform (spectrogram) of the INTEGRAL observation of GRB230307A. The transform shows transient power at low frequencies in the first ∼20 seconds or so of the burst, where the variability is particularly strong. It also shows a short, transient signal between 0 − 10 s at 1.2 Hz, similarly to what was identified in the Fourier periodogram. The candidate signal at 0.32 Hz identified in the Fourier periodogram is less apparent here. Right: Fourier periodogram (black) and wavelet periodogram (blue) with the candidate signals found in the Fourier analysis noted as dashed orange lines. The Fourier and wavelet periodograms largely match.