IEEE 661-1979 (R2008) pdf free

04-26-2021 comment

IEEE 661-1979 (R2008) pdf free.IEEE Standard Method for DeterminingObjective Loudness Ratings of Telephone Connections.
The methods that are used to measure thetransmission performance of telephone connec-tions may be divided into two classes: objectivemethods and subjective methods.This standardconsiders an objective method that can be usedfor measuring telephone connections in a man-ner that reflects the subjective attribute of loud-ness with an accuracy suitable for most tele-phone transmission engineering problems. Theperformance measure is expressed in terms of adefined reference and is referred to as an objec-tive loudness rating.
The objective method utilizes a sound sourceto activate the telephone transmitter,and anacoustic coupler and associated microphone(artificial ear) as an acoustic termination forthe telephone receiver.The sound source con-sists of a source of electric energy , a specialty pe of loudspeaker unit (artificial mouth),and such supplementary electric and acous-tic components as may be required so thatthe ensemble provides a controlled sound field.The artificial mouth and artificial ear providea simpler means of measuring characteristics oftelephone connections than is possible with thehuman mouth and ear. The practical design ofartificial mouths and artificial ears is such thatthey only approximate their respective humancounterparts. Thus telephone connection char-acteristics measured using these devices willonlyapproximate and not duplicate thosecharacteristics measured with human mouthsand ears. However, experience has shown thatcharacteristics determined using these devicesare highly useful in telephone transmissionengineering.
Subjegtive methods for rating the transmis-sion performance of telephone connectionsinvolve human talkers and listeners. Commonly used subjective test methods include thosebased on loudness assessment,articulation,and judgment.[1-4].’ The particular methodemployed in any given situation depends onthe transmission parameter(s) to be evaluatedand on the performance measure criterion ofinterest, for example, articulation or loudness.Subjective methods have the particular ad-vantage that ratings obtained are direct meas-ures of performance. A major disadvantage ofsubjective methods is that they often requirelarge groups of human subjects for long timeperiods in order that the results have signifi-cance.Objective methods,on the other hand,involve somewhat simpler and better controlledmeasurements,and a large number of measure-ments can be made in a relatively short periodof time. Moreover,measurements can be ob-tained that reflect subjective evaluation withsuitable accuracy.
This standard is concerned with a specific ob-jective method of determining the loudnessratings of telephone connections.The methodis based on objective measurements and com-putations performed in such a manner that thenumerical results obtained reflect the subjec-tive attribute of loudness.IEEE 661 pdf download.

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