Subject: Re: Traveling waves or resonance? From: "Richard F. Lyon" <DickLyon(at)ACM.ORG> Date: Fri, 15 Oct 2004 22:27:26 -0700>Some years back this list began a discussion on the relative virtues of >viewing the cochlea as driven by traveling waves or resonance. Happily, >progress has been made in my endeavours to revive a resonance theory of >hearing and an approachable discussion piece on the subject has just been >published in PLoS Biology. The reference is > >Bell A (2004) Hearing: Travelling Wave or Resonance? PLoS Biol 2(10): e337. >The open-access, full-text article is at >http://dx.doi.org/10.1371/journal.pbio.0020337 Andrew, That is indeed an approachable piece, very well written and produced. But I'd like to disagree with it anyway. A few points for now. First, you say of Gold that "In fact, the abstract of his 1948 paper declares that Œprevious theories of hearing are considered, and it is shown that only the resonance theory of HelmholtzŠ is consistent with observation¹." But did he mean to include the traveling wave theory in that? Von Békésy¹s book was 1960, so he certainly wasn't reacting to that. And nodoby had an active traveling wave theory yet, so he couldn't be including there. And many ohters have concluded that the theory of Helmholtz is NOT consistent with what we know of hearing. Second, the "regenerative" idea is not the only way to get a big active gain. In fact, it has the trouble of being only an extremely narrow-band way to get gain. The first really high-gain high-bandwidth electronic amplifier was the invention of Rudy Kompfner and John Pierce known as the travelling-wave-tube amplifier. It used a travelling wave in an active medium (a beam of moving electrons in this case) to get high gain over a wide band, without feedback. Take a look at that idea, and I think you'll see that it's a better analog of the cochlea than the idea of "resonance" is. Third, sharp threshold tuning curves are an epiphenomenon. If you look at output of a hair cell or neuron versus frequency, for a constant input power or amplitude or velocity or anything else, you do NOT get a very sharp curve. Von Békésy¹s "lateral inhibition" went a long way to explaining that apparent discrepancy, though it took some years of interpretation. I think Gold was brilliant and way ahead of his time, but I'm not sure he would take the position that you're taking. Dick Lyon