‘Slap back echo’ was created by Sam Phillips for Elvis Presley´s Sun recordingsand later simulated by RCA. Using cepstrum and autocorrelation, wefind that the tape delay used in Sun Studios was 134 - 137 ms, which is solong that the echo is perceived mainly as a distinct echo in the time domain,more than a coloration of timbre in the frequency domain. Even though thedelay time is long, the echo is still perceived as rather “intimate”, because theecho is in mono. Panned in stereo, the feeling of being inside a quite smallroom would disappear. The simulations by RCA, using a hallway instead oftape echo, shows somewhat shorter and less pronounced delays.