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In February 2016, a high-pitched noise was heard intermittently at night in Forest Grove, Oregon. The Department of Forestry determined that their equipment was not the cause of the sound. [1] The news about the noise was first shared with Dave Nemeyer by a Forest Grove resident, who posted a video of it on the city's Facebook page. [2]
A steel mill operated by U.S. Steel was the possible cause, but officials stated that no new equipment had been installed or activated around the time that the noise became noticeable. When the blast furnaces were deactivated in April 2020, the noise went away as well. [13] [14]
Electric traction motors often produce electromagnetically induced noise. This high-pitch noise depends on the speed and torque level of the machine, as well as the motor type. [5] Variable-frequency drives use pulse-width modulation, which introduces additional current harmonics and results in higher acoustic noise. The switching frequency of ...
The following is a list of unidentified, or formerly unidentified, sounds.All of the NOAA sound files in this article have been sped up by at least a factor of 16 to increase intelligibility by condensing them and raising the frequency from infrasound to a more audible and reproducible range.
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Roadway noise is the collective sound energy emanating from motor vehicles. It consists chiefly of road surface, tire, engine/transmission, aerodynamic, and braking elements. Noise of rolling tires driving on pavement is found to be the biggest contributor of highway noise and increases with higher vehicle speeds. [1] [2] [3]
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Noise has been associated with important cardiovascular health problems, particularly hypertension, as it causes an increase in levels of stress hormones and vascular oxidative stress. [2] [20] [21] [22] Noise levels of 50 dB(A) or greater at night may increase the risk of myocardial infarction by chronically elevating cortisol production. [23 ...