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.
Absolute pitch
Absolute pitch is more common among speakers of tonal languages, such as most dialects of Chinese or Vietnamese, which often depend on pitch variation as the means of distinguishing words that otherwise sound the same—e.g., Mandarin with four possible tonal variations, Cantonese with six, Southern Min with seven or eight (depending on dialect), and Vietnamese with six. Speakers of Sino-Tibetan languages have been reported to speak a word in the same absolute pitch (within a quarter-tone) on different days; it has therefore been suggested that absolute pitch may be acquired by infants when they learn to speak a tonal language (and possibly also by infants when they learn to speak a pitch-accent language). However, the brains of tonal-language speakers do not naturally process musical sound as language; perhaps such speakers are more likely to acquire absolute pitch for musical tones when they later receive musical training. Many native speakers of a tone language, even those with little musical training, are observed to sing a given song consistently with regard to pitch. Among music students of East Asian ethnic heritage, those who speak a tone language very fluently have a much higher prevalence of absolute pitch than those who do not speak a tone language.