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1110
140 dB Jet engine (at a distance of 25 m)
130 dB Aircraft engine (This is the treshold of pain)
120 dB Pneumatic drill
110 dB Blacksmith's hammer, concrete works
100 dB Die-cast machine
90 dB Metal workshop
80 dB Tractor
70 dB Office
60 dB Conversation
50 dB Ambient noise
40 dB Living room
30 dB Library
20 dB Bedroom
10 dB Forest, no wind
The unit of sound levels is the decibel (dB). A noise reduction of 10 dB is generally perceived as
a halving of the loudness, another 10 dB decrease halves the loudness yet again whitch corres-
ponds to a loudness reduction of 75 %, and so on.
loud
quiet
The Problem of Noise
The negative effects of noise pollution have been proven by studies, and everybody
will have experienced them at some time or another:
̈ Nervousness
̈ Lack of concentration
̈ Irritability
And these are only the most obvious effects on the human body. Noise also affects
the autonomic nervous system and can lead to permanent hearing damage.
There are a multitude of noise sources, and the individual very often has no
influence over them. The only solution when being in a noisy place is protecting
oneself against ambient noise. These noise problems are particularly prevalent in
an aircraft cockpit where a pilot often has to have the communications headset so
loud as to risk permanent hearing damage.
With the
NoiseGard
™
system, Sennheiser has come up with an effective solution.
These operating instructions explain the NoiseGard
™
principle and show you how
to use the
NoiseGard
™
headset.
Noise levels
Technische Daten NoiseGard
™
HMEC 25-KA / -CA
Kopfhörer
Wandlerprinzip dynamisch, geschlossen, ohraufliegend
Übertragungsbereich 16 Hz - 22 kHz
Impedanz aktiv/passive 200 Ohm (mono) 400 Ohm pro Seite (stereo)
Lautstärke aktiv und passiv gleich
Klirrfaktor < 1 %
Lärmdämpfung aktiv 15 dB
+ 3 dB im Bereich von 100 Hz - 2 kHz
Frequenzbereich der
aktiven Lärmdämpfung 50 - 600 Hz
Mikrofon incl. Vorverstärker
Wandlerprinzip Back-Elektret-Kondensatorkapsel,
geräuschkompensiert
Übertragungsbereich bei
einem Abstand von 2 cm 300 Hz - 5 kHz
zum Mundwinkel entsprechend DO-214
max. Schalldruckpegel 120 dB (Klirrfaktor 1 %)
Ausgangsspannung 400 mV ± 3 dB bei 114 dB aus 6 mm Abstand
(entsprechend DO-214)
Abschlußwiderstand 150 Ohm
Versorgungsspannung 8 - 16 V DC, ca 8 - 25 mA,
Beschaltung nach RTCA/DO 214
Allgemeine Daten
Kopfhörer-Andruckkraft ca 2,5 N
Gewicht ohne Kabel 170 g
Kabel einseitig, Länge gesamt: 1,8 m
Stecker HMEC25-KA: Stereo-Klinke 6,3 mm, mono beschaltet
PJ-068, 5,25 mm Mikrofon
HMEC25-CA: XLR-5
Stromversorgung 2 x 1,5 V Mignon (AA)
Alkali-Mangan Batterien (2700 mAh)
Betriebszeit ca. 20 h
Anzeige: Zweifarben-LED zur Batteriekontrolle