The Wwise Project Adventure

The Threshold defines the minimum input level (in dB) above which the HDR window top will engage.

This control has a similar behavior to the ratio control in an audio compressor. The HDR window top attenuates peaks that exceed the threshold while reducing the volume of quieter sounds in proportion to the ratio. For example: two sounds, one peaking at 20 dB and the other peaking at 40 dB above threshold, come out at the same level of 0 dBFS, as long as they are not played at the same time. The difference between the two is that the former will result in an attenuation of -20 dB to sounds below threshold, while the latter will result in an attenuation of -40 dB.

At lower ratios, say 4, a sound peaking at +20 dB comes out at +5 dB, while a sound peaking at +40 dB comes out at +10 dB. The attenuation that results on sounds below threshold in these examples is -15 dB and -30 dB respectively. Using lower ratios is therefore useful to gain back "global" dynamic range for sounds above threshold that are otherwise taken away by the HDR system. The drawback is that sounds may peak above threshold, so you need to keep sufficient headroom after the HDR bus to avoid clipping. This can be done by setting the HDR bus volume to a value lower than 0 dB (for example, -10 dB).

The Release time defines the rate at which the HDR window falls back to rest when the target is below the current value. In Linear Mode, it is the time in seconds it takes to fall by approximately 10 decibels. In Exponential Mode, it is the time in seconds it takes to reach approximately 0.37 (1/e) of the difference between the target and the current value. To know which mode to choose, you need to decide which sounds best based on your source material and game type.