Method and apparatus for level control in blending an audio signal in an in-band on-channel radio system

A method for processing a digital audio broadcast signal, the method comprising:

• (a) separating an analog audio portion of the digital audio broadcast signal from a digital audio portion of the digital audio broadcast signal;
• (b) determining a loudness of the analog audio portion over a first short time interval;
• (c) determining a loudness of the digital audio portion over the first short time interval;
• (d) using the loudness of the analog audio portion and the loudness of the digital audio portion to calculate a short term average gain;
• (e) determining a long term average gain;
• (f) converting one of the long term average gain or the short term average gain to dB and providing the converted average gain to an audio processor;
• (g) if an output of a receiver has been blended to digital, adjusting a digital gain parameter toward the long term average gain by a preselected increment to produce an adjusted digital gain parameter;
• (h) if the output of the receiver has not been blended to digital, setting the digital gain parameter to the short term average gain;
• (i) providing the digital gain parameter adjusted by step (g) or step (h) to the audio processor;
• and
• (j) repeating steps (a) through (i) using a second short time interval.