The distance where sound either becomes inaudible or stops attenuation, depending on the rolloff mode.
AudioRolloffMode.Linear: For the linear rolloff mode, the maxDistance is the point where the volume reaches zero and the sound becomes inaudible.
AudioRolloffMode.Custom: For the custom rolloff mode, the maxDistance sets the distance bounds of the curve. Any distance beyond holds the last available value.
AudioRolloffMode.Logarithmic: For the logarithmic rolloff mode, the audio source ignores this setting. The sound will continue to attenuate with distance indefinitely.