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The report "A Review of Published Research on Low Frequency Noise and its Effects" [54] contains a long list of research about exposure to high-level infrasound among humans and animals. For instance, in 1972, Borredon exposed 42 young men to tones at 7.5 Hz at 130 dB for 50 minutes.
Its contribution to total noise is characterized by the corner frequency f c between the low-frequency region dominated by flicker noise and the higher-frequency region dominated by the flat spectrum of white noise. MOSFETs have a high f c (can be in the GHz range). JFETs and BJTs have a lower f c around 1 kHz, [3] but JFETs usually exhibit ...
Low frequency (LF) is the ITU designation [1] [2] for radio frequencies (RF) in the range of 30–300 kHz. Since its wavelengths range from 10–1 km , respectively, it is also known as the kilometre band or kilometre waves .
Spectrum analyzer based measurement can show the phase-noise power over many decades of frequency; e.g., 1 Hz to 10 MHz. The slope with offset frequency in various offset frequency regions can provide clues as to the source of the noise; e.g., low frequency flicker noise decreasing at 30 dB per decade (= 9 dB per octave). [3]
Radio noise near in frequency to a received radio signal (in the receiver's passband) interferes (RFI) with the operation of the receiver's circuitry.The level of noise determines the maximum sensitivity and reception range of a radio receiver; if no noise were picked up with radio signals, even weak transmissions could be received at virtually any distance by making a radio receiver that had ...
Extremely low frequency (ELF) is the ITU designation [1] for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. [2] [3] In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 kHz.
Notch filters – Notch filters or band-rejection filters are useful for eliminating a specific noise frequency. For example, power lines within a building run at 50 or 60 Hz line frequency. A sensitive circuit will pick up this frequency as noise. A notch filter tuned to the line frequency can remove the noise.
The f c for an amplifier depends on the actual configuration used, because radio-frequency and low-frequency negative feedback can have an effect on f c. So for accurate results, f c must be determined from added noise measurements on the amplifier using R.F., with the actual circuit configuration to be used in the oscillator.