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.
Contemporary architecture
The Elbphilharmonie concert hall in Hamburg, Germany, by Herzog & de Meuron, which was inaugurated in January, 2017, is the tallest inhabited building in the city, with a height of 110 meters (360 ft). The glass concert hall, which has 2100 seats in Vineyard style, is perched atop a former warehouse. One side of the concert hall building contains a hotel, while the structure on the other side above the concert hall contains forty five apartments. The concert hall in the middle is isolated from the sound of the other parts of the building by an "eggshell" of plaster and paper panels and insulation resembling feather pillows.