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Re: [Phys-L] non-linear ears.

Students love testing their own hearing.
Use good closed cell over the ear headphones <>
Many speakers and pretty much every laptop speaker won’t work at 80kHz.

Dan M

On Oct 29, 2020, at 23:03, Jeff Bigler <> wrote:

This is only tangentially related, but when I teach sound to my high school physics classes, I show a diagram of the inner ear, with estimates of where different frequencies hit the Basilar membrane. I talk about how as we age, we lose the ability to detect sounds that hit the membrane near the end. Then I get out a frequency generator and set it for about 1000 Hz, asking students to raise their hand if they can hear the tone, and to keep it up while they can still hear it and put it down when they are no longer able to.

As expected, my 55-year-old ears cut out around 13 kHz. Most of my 16-18-year-old students can typically hear up to about 18-20 kHz, but every year I have one or two who can hear up to about 40 kHz. A few years ago I had a student who could hear up to almost 80 kHz. (I turned the knob slowly back and forth to confirm, and her hand went up and down reliably at the same point.) I asked her whether she could hear noise from things like CRTs, fluorescent lights, etc. She confirmed that she always heard these things, but for her whole life up to that point everyone told her that she was wrong and that she was just imagining it.

Jeff Bigler
Physics & Chemistry Teacher, NBCT
Lynn English High School; Lynn, MA

On 10/28/2020 6:24 PM, Brian Whatcott wrote:
Ah Bernard: your experimental days are not past! If you use just one ear piece and you are deaf in the other, you will have no opportunity to test the "neural processing" mix that John Denker pointed to.You will be able to detect the augmented fourth in question however, if the effect grows stronger with tone amplitude and the tones encounter some non-linearity in the audio amplifier feeding your ear-piece.A similar experimental procedure for people with binaural hearing involves getting progressively closer to the two audible tone source - a progressively more pronounced effect suggests the known non-linear response of the basal membranes.
On Wednesday, October 28, 2020, 03:57:32 PM CDT, bernard cleyet via Phys-l <> wrote:
Now I wish I’d heard or thought of that. Back in 1959 for a Psych. paper (Psy. 1, UCSB), having only one oscillator I recorded (and played) one tone (1/4” tape) and operated the oscillator at various frequencies to hear the Tartini tritones. A friend who recorded the student recitals at the Music Academy of the West (Lotte Lehman’s) assisted (his recorder!) He had good hearing, so identified the notes.

bc suffering nostalgia.

On 2020/Oct/09, at 16:29, John Denker via Phys-l <> wrote:

Tangentially related: Nonlinear auditory cortex.

You can play sine waves of two different frequencies, one in each ear,
and hear the beat note.

This has been known in the literature for eons. It shoots down a great
many simplistic theories about how the auditory system works.

See e.g. the following, and references therein:
Forum for Physics Educators
Forum for Physics Educators
Forum for Physics Educators

Forum for Physics Educators