Hi Andy,I believe the ear drum maxes out at 20kHz.#1: the cochlear envelope gets inputs in addition to the ear drum.They mostly modify the conversion from sense (electromagnetic energy) to neuron output, but also direct cochlear vibration produces modification. Also, there are other types of auditory input in addition to vibration. Think time-impulse, not tonal-frequency.
#2: False assumption. Brain gets inputs from cochlear cilia (hairs) which can be stimulated various ways. Plus additional inputs (beyond cochlear cilia). It is known that video input affects the ear (dizziness from spinning alters sound perception) and bright lights (strobes affect hearing), and so on. The brain is a parallel processor.
#3: Probably mostly true, but the ear-drum-stirrup system obeys the mass-stiffness-damping physical laws and therefore falls off rapidly above its upper resonance. And I don't know how much importance to assign to the residuals. Psychological damage can be inflicted via super-sonic sound that is not knowingly heard. On the other hand, there are thresholds below which we don't knowingly hear, and there are masks where we become unaware of sound beyond some marker, such as a resonance frequency or FR hump. More questions than answers.
#4 ( A lot of people). That's a good example. Sound below about 20Hz is sensed via the solar plexus (chest-diaphragm) as well as mastoid process (skull behind ears) and forehead. The head bones directly modify the cochlear response, but the solar plexus couples directly with the right-brain auditory cortex, with speculation about other skin-body involvement.
Historical note: The Germans developed a sub-sonic technology in the 3 to 5 Hz range to play before Hitler took stage. People puked, fainted and became agitated. As he took stage, they stopped the signal for a state of comparative euphoria. These low frequency tones can be lethal, infra-sonic but definitely directly related. Horses can "hear" a train more than 5 miles down the track. They sense that 4Hz wave through their hooves. I mention these things as examples among many to illustrate that hearing is complex beyond 20Hz to 20kHz eardrum vibration.
#2: False assumption. Brain gets inputs from cochlear cilia (hairs) which can be stimulated various ways. Plus additional inputs (beyond cochlear cilia). It is known that video input affects the ear (dizziness from spinning alters sound perception) and bright lights (strobes affect hearing), and so on. The brain is a parallel processor.
#3: Probably mostly true, but the ear-drum-stirrup system obeys the mass-stiffness-damping physical laws and therefore falls off rapidly above its upper resonance. And I don't know how much importance to assign to the residuals. Psychological damage can be inflicted via super-sonic sound that is not knowingly heard. On the other hand, there are thresholds below which we don't knowingly hear, and there are masks where we become unaware of sound beyond some marker, such as a resonance frequency or FR hump. More questions than answers.
#4 ( A lot of people). That's a good example. Sound below about 20Hz is sensed via the solar plexus (chest-diaphragm) as well as mastoid process (skull behind ears) and forehead. The head bones directly modify the cochlear response, but the solar plexus couples directly with the right-brain auditory cortex, with speculation about other skin-body involvement.
Historical note: The Germans developed a sub-sonic technology in the 3 to 5 Hz range to play before Hitler took stage. People puked, fainted and became agitated. As he took stage, they stopped the signal for a state of comparative euphoria. These low frequency tones can be lethal, infra-sonic but definitely directly related. Horses can "hear" a train more than 5 miles down the track. They sense that 4Hz wave through their hooves. I mention these things as examples among many to illustrate that hearing is complex beyond 20Hz to 20kHz eardrum vibration.