IEC 61842-2002 pdf – Microphones and earphones for speech communications

IEC 61842-2002 pdf – Microphones and earphones for speech communications.
3.1.2 headset assembly for speech communications, which consists of a holder to put on the talker’s head, one or two earphone parts and a microphone part, so as to keep the talker’s hands free 3.1.3 earset assembly for speech communications, which consists of an earphone part and a microphone part, so as to keep the talker’s hands free, without a holder to put on the talker’s head NOTE The distinction between an earset and a headset is as complicated as it is between an earphone and a headphone. Table 1 explains the definitions of earphone, headphone, earset and headset used in this standard. 3.1.4 microphone for speech communications: a) part of a handset, an earset or a headset, which functions as a microphone (an acousto- electrical transducer) b) assembly of a microphone unit for speech communications and a case for measurement purposes, including acoustical circuit elements so as to obtain practical frequency characteristics NOTE 1 A microphone for speech communications is understood to include devices, if any, such as amplifiers or impedance matching transformers up to the output terminals. NOTE 2 A microphone for speech communications is called merely “microphone”, or “microphone part” of a handset, of an earset or of a headset, in Clause 4 of this standard and beyond. 3.1.5 earphone for speech communications a) part of a handset, an earset or a headset, which functions as an earphone (an electro- acoustic transducer) b) assembly of an earphone unit for speech communications and a case for measurement purposes, including acoustical circuit elements so as to obtain practical frequency characteristics NOTE 1 Any component which is intended by the manufacturer as an integral part of the earphone is included during measurements. NOTE 2 An earphone for speech communications is called merely “earphone”, or “earphone part” of a handset, of an earset or of a headset, in Clause 4 of this standard and beyond.
3.2 Devices for measurement 3.2.1 mouthpiece holes holes bored into the front of the enclosure of a microphone unit for speech communications, to receive the input sound 3.2.2 earcap holes holes bored into the front of the enclosure of an earphone for speech communications, to radiate the output sound 3.2.3 artificial mouth sound source for microphone measurement, which can produce the sound field similar to that around an ordinary human mouth 3.2.4 artificial ear acoustic load for earphone measurement, whose acoustic impedance is similar to that of an ordinary human ear. It includes a microphone for measurement 3.2.5 lip ring circular ring placed in front of the sound outlet of an artificial mouth for localizing the equivalent lip position 3.2.6 lip plane outer plane of the lip ring, giving the reference point for finding the measuring position 3.2.7 external d.c. power supply d.c. power supply for a microphone for speech communications including an amplifier or an electrical impedance converter circuit 3.2.8 additional resistance electrical resistance for the earphone for speech communications which requires an external resistance for necessary adjustment of characteristics of the device 3.2.9 probe coil coil for measurement of the external magnetic field of an earphone for speech communications 3.3 Characteristics and performance 3.3.1 sensitivity (V/Pa) absolute value of the ratio between the open-circuit output voltage from a microphone for speech communications placed at a specified point in the sound field produced by the artificial mouth and the sound pressure in the undisturbed free field at a specified calibration point, the signal frequency being the reference frequency NOTE Though the specified point for the microphone and the sound pressure calibration point should be identical in general, these points may be different according to this Standard.
4.2.9 Rated impedance (Ω) Absolute value of the electrical impedance of a microphone or earphone for speech communications. For an earphone with an electrodynamic transducer, it is recommended that the value is chosen so that the lowest value of the modulus of the actual impedance within the rated frequency range is not less than 80 % of the chosen value. Alternatively, it may be given as the value at the reference frequency or the value at the frequency specified by the manufacturer. 4.2.10 Rated capacitance (nF) The capacitance of an earphone for speech communications at the frequency specified by the manufacturer, or at 120 Hz, if not specified. 4.3 Measuring conditions 4.3.1 Environmental interference The level of disturbances due to environmental noise, reverberation, wind noise, electro- magnetically induced noise, vibration noise and other interference shall be at least 10 dB below the measured quantity. 4.3.2 Reference sound pressure The reference sound pressure for a microphone shall be 1 Pa and that for an earphone shall be 20 µPa. 4.3.3 Signal for measurement A sinusoidal signal shall be used for measurement unless otherwise specified. Results may also be gained from measurements using noise signals, quasi-random sequence signals or impulsive signals. If signals other than sinusoidal signals are used, it is the responsibility of the test house to show that the results are equivalent or have fewer artefacts than those obtained with sinusoidal signals. 4.3.4 Reference frequency and frequency range The reference frequency shall be 1 kHz. The frequency range shall be from 150 Hz to 5 kHz unless otherwise specified. The frequency values for measurement at discrete frequency points shall be specified by the manufacturer.