Controlling analogue gain using digital gain estimation

A method for controlling gain applied to an audio signal, the method comprising:

• estimating the power of a digital signal derived from the audio signal;
• determining, in dependence on the estimated power, a digital gain which would modify the power of the digital signal so as to reach a target power level;
• and
• adjusting an analogue gain applied to the audio signal, in dependence on the determined digital gain, from a current gain level to an adjusted gain level at an adjustment rate, the rate being determined in dependence on the power difference between the digital signal power and the target power level;
• wherein the adjustment rate is variable and the adjustment rate is increased in response to determining an increase in the power difference between the digital signal power and the target power level or the adjustment rate is decreased in response to determining a decrease in the power difference between the digital signal power and the target power level.

A non-transitory computer readable storage medium having stored thereon a computer readable description of an integrated circuit that, when processed in an integrated circuit manufacturing system, causes the integrated circuit manufacturing system to manufacture a gain control system for controlling gain applied to an audio signal wherein the gain control system is embodied in hardware on an integrated circuit, the system comprising:

• a power estimator configured to estimate the power of a digital signal derived from the audio signal;
• a digital gain estimator configured to determine, in dependence on the estimated power, a digital gain which would modify the power of the digital signal so as to reach a target power level;
• and
• a gain controller configured to adjust an analogue gain applied to the audio signal, in dependence on the determined digital gain, from a current gain level to an adjusted gain level at an adjustment rate, the rate being determined in dependence on the power difference between the digital signal power and the target power level;
• wherein the adjustment rate is variable, and the gain controller is configured to
• increase the adjustment rate in response to determining an increase in the power difference between the digital signal power and the target power level, or
• decrease the adjustment rate in response to determining a decrease in the power difference between the digital signal power and the target power level.