Nintendo DMG-01 - Game Boy Console Manual page 29

TM
Game Boy CPU Manual
When the All Sound OFF flag (bit 7 of NR52) is set to
0, the mode registers for sounds 1,2,3, and 4 are
reset and the sound output stops. (NOTE: The setting
of each sounds mode register must be done after the
All Sound OFF mode is cancelled. During the All Sound
OFF mode, each sound mode register cannot be set.)
NOTE: DURING THE ALL SOUND OFF MODE, GB POWER
CONSUMPTION DROPS BY 16% OR MORE! WHILE YOUR PROGRAMS
AREN'T USING SOUND THEN SET THE ALL SOUND OFF FLAG TO
0. IT DEFAULTS TO 1 ON RESET.
These tend to be the two most important equations in
converting between Hertz and GB frequency registers:
(Sounds will have a 2.4% higher frequency on Super
GB.)
gb = 2048 - (131072 / Hz)
Hz = 131072 / (2048 - gb)
by DP
2.9. Sound
Page 29