Harman Kardon
In 1959, Harman Kardon marketed the Citation II, an early ultra wideband stereophonic tube amplifier. Designed by Stewart Hegeman, it featured 60 watts/channel output with a frequency response of 18-60,000 Hz at 20 watt output. The company promoted their philosophy of designing high fidelity sound using amplifiers that provided widest possible audio bandwidth. Although the human ear highest audible range is around 20,000 Hz, the full range of sound goes beyond that with harmonics and overtones that may be beyond the hearing range of the human ear. These harmonics interact with other frequencies to produce audible secondary sounds or interference. Harman Kardon promoted the design in audio magazines and product brochures.
Evolution of the cochlea
The size of cochlea has been measured throughout its evolution based on the fossil record. In one study, the basal turn of the cochlea was measured, and it was hypothesized that cochlear size correlates with body mass. The size of the basal turn of the cochlea was not different in Neanderthals and Holocene humans, however it became larger in early modern humans and Upper Paleolithic humans. Furthermore, the position and orientation of the cochlea is similar between Neanderthals and Holocene humans, relative to plane of the lateral canal, whereas early modern and upper Paleolithic humans have a more superiorly placed cochlea than Holocene humans. When comparing hominins of the Middle Pleistocene and Neanderthals and Holocene humans, the apex of the cochlea faces more inferiorly in the hominins than the latter two groups. Finally, the cochlea of European middle Pleistocene hominins faces more inferiorly than Neanderthals, modern humans, and Homo erectus.
Human beings, along with Apes, are the only mammals that do not have high frequency (>32 kHz) hearing. Humans have long cochleae, but the space devoted to each frequency range is quite large (2.5mm per octave), resulting in a comparatively reduced upper frequency limit. The human cochlea has approximately 2.5 turns around the modiolus (the axis). Humans, like many mammals and birds, are able to perceive auditory signals that displace the eardrum by a mere picometre.