Mute
Holding down volume or cutting a harmonic overtone of specific frequency. In the case of bass drum, it is natural to hold the mute firmly in place.
Mute Firmly	For example, I use a blanket in order to mute firmly. You can fix the blanket by putting a brick onto it. By combining this method and the loose tuning, you can produce a low tone. You can find items or materials for muting on the market.
Rehearsing	Microphones catch the sound of the bass drum. There would be no problem if you follow the instructions of engineer. Because your band members, audience, and microphone are in the opposite direction from you.