Since the beat frequency depends upon the difference between the two frequencies, you wish to go in the direction of fewer beats per second. There is no medium such as air to transmit sound on the moon. The condition where the frequency of an external force matches the frequency of an object is resonance. Gas molecules have a greater kinetic energy and move faster in warm air than in cold air. These molecules are able to transfer an impulse from one molecule to the next faster.
Longer wavelengths have lower frequencies.
Since the velocity of sound is equal to the product of the frequency times the wavelength, the velocity is a constant. The energy of the sound wave is eventually dissipated into heat. The presence and strength of various overtones determine the characteristic sound of a musical note. The sonic boom is from the building up of a pressure wave in front of the moving aircraft. Since this pressure wave is present as long as the plane is moving faster than the speed of sound, the aircraft continually makes a sonic boom.