Hi macerg,
Those red lines indicate that your wave file has clipped at those points. In other words the recording has exceeded the 0dB reference level and the samples shown as a red line have been limited to the maximum value possible.
Depending on how severe the clipping is, you may not be able to notice the effect at all. If the recording was only slightly too loud then the clipping will have only a minor effect.
Regards,
Ben