In 1960's, PCM (Pulse Code Modulation) was going into practical use for telephone transmission. Since Hitachi had failed to enter transmission business in these days, the "PCM" project started aiming the entrance to the area. The main purpose of the project was development of equipments, of course. Our Acoustics Laboratory was ordered to cooperate and help the main team. Since Hitachi's system was slightly different from the NTT's one, we were afraid that NTT's criteria might not fit to our system, so we decided to work on the transmission quality measure by ourselves. For the purpose, we developed an experimental one channel PCM system, whose parameters could easily be controlled. By changing its design parameters, such as bit number, error probability, filter bandwidths, etc, we measured the detectability of noises caused by incompleteness of PCM systems. The measurements were subjective tests, so our company hired some young girls, many of whom were middle-teens, and executed several tests.
References
T. Koshikawa and Y. Nakano: Noise Audibility Scale as
a Measure of Transmission Quality (in Japanese),
Trans. of IEC, Vol.49 [11], pp.2248-2255 (1966)
[Research Themes of Prof. Nakano.]
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First Written Before June 17, 1998
Transplanted to KSU June 17, 2003
Transplanted to So-net April 22, 2007
Last Update April 22, 2007
© Yasuaki Nakano 1998-2007