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.
Nepenthes hemsleyana
The frequency of the bats' vocalisations (starting well above 250 kHz) is the highest known of any bat species and may be an adaptation to locate pitchers among dense surrounding vegetation. The bats are likely further aided by a parabolic structure found in the rear wall of "N. hemsleyana" upper pitchers. This structure shows far stronger echo-reflection than a comparable area in the most closely related pitcher plant species, "Nepenthes rafflesiana". These reflecting structures are convergent with those of some Neotropical bat-pollinated angiosperms, such as "Marcgravia evenia".