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manual abstract
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 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 a halving of the loudness, to a loudness loud quiet HMEC 25-KA / HMEC 25-CA A headset is comprised of two units, a headphone and a microphone. The HMEC 25-KA/-CA headset is mostly used for communication in aircraft cockpits. . The microphone is a high quality back-electret condenser microphone. As per ARINC it receives its operating voltage via a connector from the aircraft . s internal power supply. . The headphone is a Sennheiser NoiseGard ™ system. This is a dynamic headphone system which, in addition to reproducing the original audio signal, electronically cancels the low frequencies of the ambient noise. This active noise compensation operates on the principle that sound and ” anti-sound“ (in phase opposition) cancel each other out. The NoiseGard ™ compensation circuitry in the headphone requires an extra power supply, so a battery compartment has been integrated into the headset cable (see illustration on the right). Clearly intelligible communication is ensured, and the pilot no longer has to turn the volume up to overcome ambient noise. NoiseGard ™ increases your comfort, but it is not a medical hearing protection! Active noise compensation with NoiseGard ™ Inserting the batteries into the battery box The NoiseGard ™ compensation circuitry is powered via a battery pack integrated into the headset cable. Insert two AA size batteries into the box as shown in the digram below. Switching the power supply on/off The on/off switch for the power supply of the compensation circuitry is at the front of the battery box. Pilot light An LED on the battery box indicates the battery status: . When the LED lights up green, the power supply for the compensation circuitry is sufficient. . When the LED is red, the batteries are almost flat and should be changed immediately. The NoiseGard ™ system is still operational. . If the LED does not light up at all when the power supply is switched on, the batteries are completely flat. The headset is still operational but without the noise compensation. The microphone is powered by the aircraft‘ s internal power supply. Thus, it is independent of the batteries and always remains operational. 1312 Noise compensation HMEC 25 Reduction/dB Frequency/Hz 20 100 1000 10000 20000 0 10 20 30 40 active passive ON/OFF LED Adjusting the microphone boom N.B. : The microphone boom is adjusted for an individual user. However, care should be taken when doing this. Once set, the boom should not be re-adjusted. If it is continually flexed it is liable to break. Adjusting the headband Cable (worn on the right or left side) 350° Cable on the left Cable on the right N.B.: NoiseGard ™ reduces noise and increases comfort. NoiseGard ™ is not a medical noise protection system! NoiseGard ™ cannot replace an industrial ear defender system for use in noisy Volume up? - NO ! When people use headphones, loudspeakers. Listening permanent hearing NoiseGard ™ circuitry is reducing ambient noise, to more comfortable HMEC 25-CA Block Diagram boom microphone headphone capsule (left) compensation microphone (left) compensation microphone (right) headphone capsule (right) compensation circuit (right) battery box 5-pin XLR plug microphone amplifier compensation circuit (left) HMEC 25-KA Block Diagram 3-pin plug 3-pi...
Other models in this manual:Wireless Accessories - HMEC 25-KA (813.05 kb)