File:Praha-Smíchov, amplion na nástupišti.jpg
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DescriptionPraha-Smíchov, amplion na nástupišti.jpg |
English: A public address horn speaker in a train station in Smíchov, Prague, the Czech Republic. This type of speaker, called a reflex or reentrant horn, or bullhorn, is a type of horn loudspeaker. Horns are widely used as speakers in public address systems because they are more efficient, typically able to produce 10 times the sound energy of cone speakers from a given amplifier output. In this type of speaker, a small metal diaphragm is vibrated by an attached coil of wire in a magnetic field, creating sound waves, which are conducted to the outside air through a flaring acoustic horn duct. Since the horn must be several feet long, to make it more compact the sound path is "folded" into a zigzag pattern, with the sound passing through a narrow central duct to a concentric backward duct, and then out through the flaring outer horn. Bullhorns have very poor frequency response, typically from 300-400 Hz to 5 kHz. However this can actually be an advantage in public address systems, since it matches the frequency distribution of the human voice, any background noise outside this bandwidth is attenuated.
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Date | |||||
Source | Own work | ||||
Author | ŠJů (cs:ŠJů) | ||||
Permission (Reusing this file) |
I, the copyright holder of this work, hereby publish it under the following license: ![]() ![]() ![]() This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
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Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 10:59, 29 March 2010 | 3,264 × 2,448 (890 KB) | ŠJů (talk | contribs) | {{Information |Description= {{cs|cs:Praha-cs:Smíchov. Nádraží Praha-Smíchov, nádražní amplion na 3. nástupišti.}} {{en|en:Smíchov, en:Prague, the Czech Republic. Train station, a standing megaphone |
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Camera manufacturer | EASTMAN KODAK COMPANY |
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Camera model | KODAK EASYSHARE Z8612 IS Digital Camera |
Exposure time | 1/40 sec (0.025) |
F-number | f/3.2 |
ISO speed rating | 125 |
Date and time of data generation | 09:45, 28 March 2010 |
Lens focal length | 13.2 mm |
Orientation | Normal |
Horizontal resolution | 480 dpi |
Vertical resolution | 480 dpi |
File change date and time | 09:45, 28 March 2010 |
Y and C positioning | Centered |
Exposure Program | Not defined |
Exif version | 2.21 |
Date and time of digitizing | 09:45, 28 March 2010 |
APEX shutter speed | 5.3333333333333 |
APEX aperture | 3.4 |
APEX brightness | 0 |
APEX exposure bias | 0 |
Maximum land aperture | 3.4 APEX (f/3.25) |
Metering mode | Pattern |
Light source | Unknown |
Flash | Flash did not fire, compulsory flash suppression |
DateTimeOriginal subseconds | 35 |
Color space | sRGB |
Exposure index | 125 |
Sensing method | One-chip color area sensor |
Custom image processing | Normal process |
Exposure mode | Auto exposure |
White balance | Auto white balance |
Digital zoom ratio | 0 |
Focal length in 35 mm film | 78 mm |
Scene capture type | Standard |
Contrast | Normal |
Saturation | Normal |
Sharpness | Normal |
Subject distance range | Unknown |
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28 March 2010
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