Cube (algebra) however, easy to show that most numbers are not perfect cubes because "all" perfect cubes must have digital root 1, 8 or 9. That is their values modulo 9 may be only −1, 1 and 0. Moreover, the digital root of any number's cube can be determined by the remainder the number gives when divided by 3: Every positive integer can be written as the sum of nine (or fewer) positive cubes. This upper limit of nine cubes cannot be reduced because, for example, 23 cannot be written as the sum of fewer than nine positive cubes: The equation has
G.729 goes quiet because of no speech, the receiving side might assume that the link has been cut. By inserting comfort noise, analog hiss is simulated digitally during silence to assure the receiver that the link is active and operational. G.729 Annex J, maintained by G.729.1, provides support for wideband speech and audio. It defines variable bit-rate wideband enhancement using up to 12 hierarchical layers. The core layer is an 8 kbit/s G.729 bitstream, the second layer is a 4 kbit/s narrowband enhancement layer, and the third 2 kibt/s layer is a bandwidth enhancement layer. Further layers provide wideband enhancement in