signals in the infrasound part of the sound spectrum the tones are so low frequency that our ears can't pick them up. manta rays send acoustic messages underwater by beating their wing like fins we don't hear those signals either. that's in contrast to the noise the migratory geese and cranes make during their long journey. the birds constantly call back and forth that helps them keep track of their young in the air and tells them whether the lead bird needs to be relieved calling costs energy but saves energy for the formation overall. by the way the calls of a single crane are roughly as loud as those of a human weighing in around sixty decibels.