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FAQ

• What are NRR (Noise Reduction Ratings) for a headset?

  NRR (Noise Reduction Ratings) is a rating of the passive reduction of a headset and this is by a set standard (ANSI).

  However there are no present standards for measuring ANR (Active Noise Reduction). Each Manufacturer uses their own standards. Sennheiser uses the standards and results of an independent laboratory that is accredited by the National Institute of Standards and Technology. One should be very careful in assuming that all manufacturers use these results in a fair and unbiased way.

  
  
  
• Which accessories come with my ATC/C3 headset purchase?

  Your purchase of a Sennheiser ATC/C3 headset will include a windscreen, clip, bag, and manufacturer certificates.

  
  
  
• Active Noise Cancellation

  Active noise cancellation is the reduction of noise, particular in the low frequency range, by using active noise compensation electronic circuitry. Active noise cancellation is measured in decibels (dB).

  
  
  
• Caliper Pressure (Contact Pressure)

  Caliper Pressure (sometimes referred to as Contact Pressure) is the amount of force applied to the sides of the head while wearing headphones. Caliper pressure is measured in Newton’s (N) and could range from 1.6 N (loose fit) to 10 N (snug fit).

  A tight coupling between the headphone and the ear is necessary in order to maximize passive attenuation however too much pressure can make the headphone uncomfortable to wear for long periods of time. 

  
  
  
• Condenser Microphone (Electret Microphone)

  A CONDENSER or ELECTRET microphone is one that is based on an electrically charged diaphragm (or back plate) assembly which forms a sound-sensitive capacitor.

  On a condenser or electret microphone a very thin metal or metal coated-plastic diaphragm is mounted just in front of a ridged metal or metal-coated-ceramic back plate. This assembly is known as a capacitor (condenser) which has the ability to store a charge or voltage. When the element is charged an electrical field is created between the diaphragm and the back plate proportional to the spacing between them. Sound waves vibrate the diaphragm and it is the vibration of this spacing due to the motion of the diaphragm relative to the back plate that produces the electrical signal corresponding to the sound picked up by a condenser microphone. 

  The construction of a condenser microphone must include some provision for maintaining the electrical charge or polarizing voltage.

  NOTE: An Electret condenser microphone has a permanent charge maintained by a special material (Electret) deposited on the back plate or on the diaphragm.

  
  
  
• Diaphragm

  The diaphragm is a  thin membrane in a microphone which moves in response to sound waves.

  
  
  
• Dynamic Microphone

  A DYNAMIC microphone employs a diaphragm/voice coil/magnet assembly which forms a miniature sound-driven electrical generator.

  Sound waves strike a thin plastic membrane (diaphragm) which vibrates in response. A small coil of wire (voice coil) is attached to the rear of the diaphragm and vibrates with it. The voice coil itself is surrounded by a magnetic field created by a small permanent magnet. It is the motion of the voice coil in this magnetic field that generates the electrical signal corresponding to the sound picked up by a dynamic microphone.

  Dynamic microphones have a simple construction and are economical and rugged. They can provide excellent sound quality and good specifications in all areas of microphone performance. They handle extremely high sound levels and it is almost impossible to overload a dynamic microphone.

  Dynamic microphone are relatively unaffected by extremes of temperature humidity.

  
  
  
• Gain

  Gain is the amount of increase in audio signal strength. Gain is often expressed in decibels (dB).

  
  
  
• Microphone Gain Control

  Microphone Gain Control is a  level control on a microphone preamplifier that sets gain and is used to prevent overload of a preamplifier.

  
  
  
• Output Voltage

  Output Voltage is similar to sensitivity except it takes into account additional electronics used to amplify the signal. This is typically measured over a range of frequencies and will include the term + or - 3 dB. Rather than using 1 Pascal this specification may also include the input level used such as 114 dB at a distance of 6 mm.

  
  
  
• Passive Attenuation

  Passive attenuation is the ability of the headset to reduce the ambient noise level by merely wearing the headset without the aid of any electronic assistance (ie: active noise compensation circuitry). Passive attenuation is measured in decibels (dB).

  
  
  
• Pre-Amp

  A Pre-Amp is a low-noise amplifier designed to take a low-level signal (such as that from a microphone) and bring it up to normal line level.

  
  
  
• Sensitivity

  Sensitivity  is a measurement of how much voltage is produced by a microphone for a specific measured input (1 Pascal). Sensitivity is measured in micro volts (uV) or millivolts (mV).

  A typical rating for a dynamic microphone would be 1 mV. A typical rating for an Electret microphone would be 3.5 to 10 mV A typical rating for an Electret with amplifier would be 170 mV. 

  The higher the number the stronger the signal produced by the microphone.

  
  
  
• XLR-3 Connector

  The XLR-3 Connector is a single connector that can be used in place of the PJ055 headphone and the PJ068 microphone plugs on some Sennheiser headsets.

  Pin 5 of this plug can also be used to provide aircraft power for the NoiseGard power supply on some Sennheiser headsets.

  
  
  
• XLR-5 Connector

  The XLR-5 connector is a single connector that can be used in place of the PJ055 headphone and the PJ068 microphone plugs on some Sennheiser headsets.

  Pin 5 of this plug can also be used to provide aircraft power for the NoiseGard power supply on some Sennheiser headsets.