Inspire provides two input types: Sinusoid (Tonal) and Speech. With a Sinusoid Input, the level is equal in dB SPL at every frequency, and the instrument sees only one frequency at a time. With Speech Input, the overall level is the sum of speech energy at all frequencies. While the displays may differ, gain, as a function of frequency, will be the same for sinusoidal and speech inputs.
To further illustrate the difference, consider the following example. For a Sinusoid Input, a 50 dB SPL sinusoid input will yield an output of (50 dB + gain) at every frequency. In contrast, for Speech Input, a 50 dB SPL speech input will yield a variable output at each frequency because it is based on the Long Term Average Speech Spectrum (LTASS). The LTASS is the average level of speech measured in narrow frequency bands. Since the speech spectrum is not flat but falling, the input level and the resulting output curve also drops.
Inspire defaults to Speech Input for all displays.
The display type can be changed from the Display
menu
or with a right mouse click on any frequency response curve 
.