11
10
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:
왘
Nervousness
왘
Lack of concentration
왘
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
