Audio processing is a topic that can go many directions. I would like to briefly touch on the basic principles.
you have set up a transmitter to be able to pass the audio bandwidth, and make the positive peaks that you desire to achieve, you
must tailor the audio to fit within the boundaries of the transmitter, good engineering practices, and the receiver(s) you are trying
to cater to.
In Amplitude Modulation, there is a tremendous noise floor, and limited dynamic range. Beyond 150% positive
peaks, most receivers respond to bigger peaks as noise. This detracts from Intelligibility, and Loudness due to amplitude alone is
Loudness is perceived to be greater when the density or average percentage is increased. Generally, the
higher the average, the less bass you can run. Thus the audio will start to sound thin, or more strident. It might cut through noise
better, but at the expense of quality.
Audio processing is critical in making sure that the negative peaks do not
exceed 100% modulation. Exceeding 100% might make you sound a bit louder, but it cuts the carrier off at an audio rate, causing splatter.
Also, it creates more area under the curve causing RMS Watt meters to read higher than they should. Looking at an oscilloscope will
show this as the Peak to Peak does not change, but the RMS meter keeps climbing (More on the Scope in another section). Also, the
flat topping of positive peaks will increase area under the curve.
The idea of audio processing is to control the
audio in a manner that is acoustically pleasing, while confining it into the parameters that are defined.