Hands-on aids for the two ideas at the heart of fitting: how compression shapes loudness, and how a prescription follows the audiogram.
Compression input/output
Drag the ratio and knee to see how wide-dynamic-range compression bends the input/output curve — constant gain for soft sounds, less for loud.
Below the knee, gain is constant (the line is parallel to unity); above it, a higher ratio flattens output — packing a wide input range into the listener’s reduced dynamic range. Illustrative.
Prescription target
Set the degree of a sloping loss and watch the prescribed gain target follow it — more gain where hearing is poorer.
The target gain follows the loss — more gain where hearing is poorer. Shown with the simple half-gain rule; real procedures (NAL-NL2, DSL) also vary gain by input level. Illustrative.