The Golden Lobes and the Pinna Effect

Marshall Chasin
November 22, 2016

I just returned from the Association of Independent Hearing Healthcare Professionals (AIHHP) conference in Nottingham, England, but I didn’t see Robin Hood, or had any time to go to Sherwood Forest.  I did however give several talks about musicians, and so did our editor Brian Taylor; he spoke first and by the time I arrived in Nottingham, Brian was off having dinner with Friar Tuck or Maid Marion.

The gala event of the AIHHP conference included the Golden Lobes presentations and there were a number of them given out to AAHIP members and industry personnel who have gone far beyond the scope of their duties.  And one was given out for the best talk:  I lost and Brian won.

Incidentally the award was accepted by Dr. David Baguely on behalf of Brian (who was still off somewhere with the good Friar).  David Baguely was last year’s winner who could not be present to accept his award.  The awards were given out by the honorary president of the AIHHP- Dr. Brian C. Moore.

Nevertheless here is a picture of the loser (me) in front of two large golden pinnae cupping my ears and faking the benefits of the pinna effect.  Two things come to mind: who stores these gigantic pinnae over the year and brings them to the conference, and what would the effect be on hearing for such large sized pinnae?



Well, it turns out that these pinnae are not really made of gold and are actually a fraction of an inch thick.  Given the low density and small diameter, the effect is actually quite low- cupping your hands behind the ears would result in more of an effect. But let’s take a step back.

The pinna effect is an enhancement of the shorter wavelength (higher frequency) sounds because of the constructive interference between the incident sound entering the external ear canal and the early reflection off of the pinna (or the cupped hand).  Only the higher frequency sounds (typically above 1000 Hz) are re-enforced and enhanced because the pinnae only “see” high frequency sounds – sounds that have relatively short wavelengths.

As a rule of thumb, a sound is obstructed (and subsequently reflected) if the obstruction is on the order of ½ the wavelength of the sound.  Low frequency sounds would require obstructions that are closer to a meter, whereas higher frequency sounds reflect in the cm or mm thickness range.  The diameter of the obstruction such as the pinnae or one’s hand will define the start frequency for which all sounds above that point are enhanced, and how much depends on the density of the obstruction. 

A solid gold pinna would indeed be a wonderful reflector whereas a thin cardboard replica of a pinna would only be good for having pictures taken in front of.

In some sense this could have been another solution for Archimedes when asked by his King to determine whether an irregularly shaped crown was indeed made of gold as claimed by the royal jeweler.  Archimedes immersed the crown in a vat of water and found out how much water was displaced.  Given the known weight of the crown, Archimedes was able to determine the density (volume/weight).  I won’t tell you how the story ends other than that the royal jeweler found himself in jail later that day.

Archimedes could have held the crown up to his ear and using a probe tube microphone (with the reference microphone disabled) he could have determined the density by its reflectivity.  Somehow the crown in a vat of water story sounds better though.  I guess real ear measurement is still too new to make it into the history of science.

So, the take home message is that if you stand in front of a large pair of golden colored ears, if they do indeed enhance the sound, then they may actually be made of gold (or at least a denser material than cardboard).

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