Recently my brother sent my dad a video of the history of the Vocoder. (the Vocoder is a synthesizer that produces sounds from an analysis of speech input) Since my dad is a 30+ year veteran of AT&T and an electrical/mechanical engineer, he dropped some knowledge on my brother:
Much of this technology was also used to improve the efficiencies of the initial fiber optic trans-oceanic cables. I had been directly involved in implementing the first fiber cable (TAT-8) between the US (east coast, NY) and Europe (UK, France) as well as the Pacific ocean cables (HAW4/TPC3) to the far east (via California, Hawaii, Guam to Japan). There was limited capacity and the US telecom quality voice standard at the time was known as 64kbps per voice channel. Not too many simultaneous calls could be carried over the cable at that rate, so low bit rate technology (LBRV) was needed to be used instead to improve transmission efficiencies, which was a direct off-shoot of the Vocoder technology. The algorithm for voice frequencies vs. required bit allocation was critical for passing signals that would “sound” like a person’s normal voice but sent at a lower bit rate that would permit additional calls. Fortunately, the human ear can be “tricked” into thinking it’s hearing the original signal even though you are slipping/subtracting data bits at critically particular times and audio frequencies. I actually sampled some of the Bell Labs “blind tests” testing different bit rates and it was a fascinating experience to be at both ends of the project — lab development and my operations/engineering implementation. At the time Bell Labs was an incredibly deep and competent organization. I had several BTL engineers assigned to my team which made my life a lot easier! But back then then the technology was pure, as we called it then, “Buck Rogers”! Today, we are so many generations beyond this.
You rock, Dad.
via my brother’s site, chasing Tremendous