Making Waves: da Vinci Days lectures

What do these objects have in common (besides being part of the Benton County Museum's artifact collection)?

Answer:  They are both related to this spring's da Vinci Days programs on the theme “Making Waves.”

The first lecture, “Echoes from the Deep” (April 2) was about how marine mammals use acoustic waves for navigation, communication, and, for toothed whales, to find food. I was surprised to learn that due to temperature and pressure, there's a zone in the ocean where sound waves stay trapped in a narrow channel and do not dissipate. As a result, some whale calls can travel thousands of kilometers.  The sound waves generated by the whale's “clicks” are heard as vibrations of the jaw and fat stimulate the ears of nearby whales. The first photograph is of an ear bone from a whale in Alaska.

Speaker Dave Mellinger also showed spectrograms to illustrate the well-structured nature of humpback whale songs and sonar readings to show a pod of toothed whales locating and surrounding a school of fish.   Shipping and seismic exploration have caused a 10 decibel increase in ocean noise over the last 30 years, making whale navigation and communication more difficult. Professor Mellinger also talked about the problems of researching whales and how researchers have benefited from the acoustical research done on birds. He played a recording of whale songs sped up ten times which sounded remarkably like bird songs!

The second talk (April 9) also featured research on a hard-to-study phenomenon—spider webs.  Mechanical engineering professor Ross Hatton teamed with a biologist in California to build a mechanical web to better understand how spiders use the vibrations created by an insect landing in the web.  Spiders make the radial lines of a stiffer silk then the silk they use for the spiral lines in between.  The spider then sits in the center with its feet on the radial lines.  Vibrations are strongest from the radial lines near where the prey landed.  Also the tension is approximately the same on all spiral lines so the closer to the center the prey lands, the higher the frequency of vibration.

A conversation with engineering professor and musician ChetUdell led to adapting the research of spider web creation to make a unique electronic harp.  A computer generates notes depending upon which string is plucked. The note is determined in the same way a spider detects where its prey is trapped. The autoharp pictured above, though, generates sound from the actual physical plucking of strings of different lengths.

By Martha Fraundorf, Volunteer for Benton County Historical Society, Philomath, Oregon