It is difficult to gather information about the inside of massive stars because of degeneracies of surface characteristics such as surface temperature, brightness, etc. Recent observations of massive stars show low frequency variability in their photometric light curves, which has been interpreted as internal gravity waves (Bowman et al. 2019). Here, we estimate the typical frequency of internal gravity waves generated by convection that reach the stellar surface, including the effects of radiative diffusion. We compare the convective frequency, Brunt–Väisälä frequency and the typical frequency of damped waves, and find the latter frequency is in between the other two. We calculate the typical frequency of damped waves for main sequence stars of different masses and ages. The typical frequency of damped waves decreases as a star ages, matching the trend of the observed variability.