Before revision: For signals with impulse characteristics, echoes are perceived for delays above 50 ms. For signals with a nearly constant amplitude, the threshold of perceiving an echo can be enhanced up to time differences of 1 to 2 seconds.
After revision: For signals with impulse characteristics, echoes are perceived for delays above 50 ms. For signals with a nearly constant amplitude, the threshold before perceiving an echo can be enhanced up to time differences of 1 to 2 seconds.