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HF's position in the electromagnetic spectrum.. High frequency (HF) is the ITU designation [1] for the band of radio waves with frequency between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one hundred meters).
The higher frequency sound waves have a shorter wavelength and thus don't spread out as rapidly. For this reason, the resulting directivity of these devices is far higher than physically possible with any loudspeaker system. However, they are reported to have limited low-frequency reproduction abilities. See sound from ultrasound for more ...
An audio frequency or audible frequency (AF) is a periodic vibration whose frequency is audible to the average human. The SI unit of frequency is the hertz (Hz). It is the property of sound that most determines pitch. [1] The generally accepted standard hearing range for humans is 20 to 20,000 Hz.
Ultra high frequency: 1 m: 300 MHz: 1.24 μeV Radio waves: VHF Very high frequency: 10 m 30 MHz 124 neV: HF High frequency: 100 m 3 MHz 12.4 neV MF Medium frequency: 1 km: 300 kHz: 1.24 neV LF Low frequency: 10 km 30 kHz 124 peV: VLF Very low frequency: 100 km 3 kHz 12.4 peV ULF Ultra low frequency: 1 Mm: 300 Hz: 1.24 peV SLF Super low ...
High frequency [18] VHF: 0.03 to 0.3 GHz: Very high frequency [18] UHF: 0.3 to 1 GHz: Ultra-high frequency [18] L: 1 to 2 GHz: Long wave S: 2 to 4 GHz: Short wave C: 4 to 8 GHz: Compromise between S and X X: 8 to 12 GHz: Used in World War II for fire control, X for cross (as in crosshair). Exotic. [19] K u: 12 to 18 GHz: Kurz-under K: 18 to 27 ...
Musical sound can be more complicated than human vocal sound, occupying a wider band of frequency. Music signals are time-varying signals; while the classic Fourier transform is not sufficient to analyze them, time–frequency analysis is an efficient tool for such use. Time–frequency analysis is extended from the classic Fourier approach.
The frequency F s and the frequencies above and below it where the impedance is 1 / √ 2 Z max are important in determining the loudspeaker's T/S parameters. These can be used, for example, to design a suitable enclosure for the driver, especially for low frequency drivers. In fact F s is itself one of the Thiele/Small parameters.
It can be proven (with the help of a sum-to-product trigonometric identity) that the sum of two unit-amplitude sine waves can be expressed as a carrier wave of frequency f 1 + f 2 / 2 whose amplitude is modulated by an envelope wave of frequency f 1 - f 2 / 2 : [3]