## v0.1 (2022-05-29) Demonstrations of sound modifications to A-law and μ-law transmissions, as commonly used in ISDN, the telephony backbone, and the de-factor codec in VoIP phones. - Made a recording of The Quick Brown Fox... at normal and loud voice levels - Inserted random bits in the bits destined to carry data, causing noise - The noise level sounds like an old analog line, bearable at both levels - The noise level is clearly audible, certainly at the normal voice level - Inserted zero in the lowest bits to pause data without flag detection - The influence of these lowest bits is not audible at both levels - The data rate at the loud voice level is 27% of 64 kb/s = 17.280 kb/s - The data rate at the normal voice level is 45% of 64 kb/s = 28.800 kb/s - The data rate at complete silence level is 50% of 64 kb/s = 32.000 kb/s - Note that calls usually consist of half-time speaking (per direction) - Note that listeners are not used to silence; codecs send "comfort noise" - The experiments give rise to the work on actually inserting data frames