Question: What is loudness contour?
Answer: When doing audio frequency response equalization, a band of frequencies may need a large amount of gain/boost. The large gain will use a large amount of the processing system's dynamic range. Generally, the largest filters are applied in the low frequency range (Bass). Bass can be less noticible at lower listening levels due to the Fletcher Munson effect and needs more boost.
Many of our digital audio processors contain a loudness coutour block. This block is a group of programmable filters that can be programmed for their filter response and programmed to have their gain track the volume control. Therefore, at higher listening levels, the filters will have less gain. They will then not use as much of the processor's dynamic range and the possibility of clipping will be decreased.