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The larger the speaker, and the higher the frequency, the longer the effective nearfield. The nearfield for this device is approximately 8 metres (26 ft). [9] An LRAD can thus emit a targeted "beam" of sound at very high volume, up to 160 dB at one meter from the device. This is louder than standing behind a jet engine taking off, or a nearby ...
The ultrasonic devices achieve high directivity by modulating audible sound onto high frequency ultrasound. 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.
The U.S. Environmental Protection Agency authored a pamphlet in 1978 that suggested a correlation between low-birthweight (using the World Health Organization definition of less than 2,500 grams (88 oz)) and high sound levels, and also high rates of birth defects in places where expectant mothers are exposed to elevated sound levels, such as ...
Also, neighboring cells in the auditory cortex have similar specific frequencies that cause them to fire, creating a map of sound frequencies similar to that of the somatosensory cortex. [22] Lateral inhibition in tonotopic channels can be found in the inferior colliculus and at higher levels of auditory processing in the brain. However, the ...
Acoustic deterrent devices normally broadcast near 10 kHz and use high volume. [3] The intensity level of acoustic harassment devices has been measured up to 194 dB re 1uPa @ 1 m and the noise can be audible up to 50 kilometers away.
High-amplitude sound of a specific pattern at a frequency close to the sensitivity peak of human hearing (2–3 kHz) is used as a burglar deterrent. [ 6 ] Some police forces have used sound cannons against protesters, for example during the 2009 G20 Pittsburgh summit , [ 7 ] the 2014 Ferguson unrest , [ 8 ] and the 2016 Dakota Access Pipeline ...
Audio frequency, otherwise known as the pitch, is currently the only characteristic of sound that is known with certainty to be topographically mapped in the central nervous system. However, other characteristics may form similar maps in the cortex such as sound intensity, [ 18 ] [ 19 ] tuning bandwidth, [ 20 ] or modulation rate, [ 21 ] [ 22 ...
Ultrasonic hearing is a recognised auditory effect which allows humans to perceive sounds of a much higher frequency than would ordinarily be audible using the inner ear, usually by stimulation of the base of the cochlea through bone conduction. Normal human hearing is recognised as having an upper bound of 15–28 kHz, [1] depending on the person.