# Translations:Ricker wavelet/11/en

We see that 12 of the roots have an absolute value of unity. Any root with absolute-value unity corresponds to a two-length equal-delay wavelet in the composition of the discrete Ricker wavelet being considered. We do not like equal-delay wavelets for reasons put forth earlier in this chapter. We want all the two-length constituent wavelets to be either strictly minimum-delay wavelets or strictly maximum-delay wavelets (Robinson et al., 1978^{[1]}). We therefore modify the Ricker wavelet by adding a little bit of white noise to the center value of the autocorrelation function - say, 1% of this value - which is an operation called *prewhitening*. In other words, we multiply the center value of this autocorrelation function by 1.01. The modified Ricker wavelet now becomes

- ↑ Robinson, E. A., D. Loewenthal, and S. Treitel, 1978, Numerical testing of minimum-delay, positive- real, and positive-definite digital filters: Journal of Computational Physics,
**29**, 421–430.