21. A possible way around the problem is to use acoustic filtering, such as by resonant cavity , in the speaker setup. 22. Some pulse jet designs used a tuned resonant cavity to provide the valving action through the airflow in the system. 23. When a general shape of a resonant cavity is changed, a corresponding change in resonant frequency can be approximated as: 24. The longitudinal modes of a resonant cavity are the particular standing wave patterns formed by waves confined in a cavity. 25. A problem with resonant cavities is that a high finesse cavity has narrow cavity modes, often in the low kHz range. 26. The second factor to determine a laser's emission frequencies is the optical cavity ( or resonant cavity ) of the laser. 27. This guitar still functioned acoustically, but had a smaller resonant cavity inside, which makes less sound emit from the f holes. 28. At 1998's Burning Man, a pyrophone referred to as " Satan's Calliope " was powered by ignition of propane inside resonant cavities . 29. In the klystron, the electron beam passes through a hole in a resonant cavity which is connected to the source RF signal. 30. White's 2014 conference paper suggested that resonant cavity thrusters could work by transferring momentum to the " quantum vacuum virtual plasma ".
