Signal-to-uncertainty ratio of the BSCZ signature (see the text for the definition) in the r₀₁₀ ratios (blue curves) and the second differences (orange curves) normalised by the signal-to-uncertainty ratio observed in the frequency, according to the scaled acoustic depth of the BSCZ for KIC6679371. We note that from one star to another, this figure is very similar. The horizontal dotted line indicates where the signal-to-noise ratio of the signature of the BSCZ is equal to the signal-to-noise ratio of the frequencies. Both vertical dashed lines indicate the position of the τ_cz and 2 × τ_cz inputted in the synthetic data.