Output level/volume determines the range of a LISNR Radius Tone. In basic terms, increasing the volume increases the range, while decreasing the volume shortens the range. 

For mobile device to mobile device, average distance for Standard2 tone profile is ~20 ft and PKAB2 is ~3ft. This range can be increased with external speakers to increase the volume.

For more specific information on Radius Tone Profiles, check out this article.