Sound-pressure level (SPL) fluctuation caused by air conditioners is measured using pure tones as the sound source, in a gymnasium. When the air conditioner is turned on, the mean standard deviation of SPL changes about 0.9 dB at 2 kHz, 2.5 dB at 4 kHz, 3.3 dB at 8 kHz, and 3.8 dB at 16 kHz, while that in the case with air conditioning off is less than 0.6 dB at all frequencies. The cumulative density of mean-squared amplitude corresponds well with the gamma distribution. Based on this statistical analysis, the SPL change is thought to be related to the impulse response which is represented by the direct sound (regular) and changing delay time of reflection sound (irregular). The cumulative density of mean-squared amplitude for this model using pure tones also indicated a gamma distribution. It is found that the frequency characteristic and the cumulative density of the SPL change have the same tendencies as the method of modulation for the delay time of reflected sound.