In order to reduce gas consumption and background noise of large power pneumatic loudspeaker, YANG Yichun and TENT Pengxiao of Key Laboratory of Noise and Vibration Research, CAS Institute of Acoustics carried out a series of studies and provided a modulation method of the flow control to perform advanced sound performance and high effectiveness with large gas-sound ratio.

First, they studied a full modulation in a model to find its principle of sound generation by gas form horn throat. According to this model, they adjusted the modulator of pneumatic loudspeaker in non-flow when in static state. Sound wave is pre-processed to cut its lower envelope to form a new signal to control the gas-flow. This flow is proportional to sound's amplitude. The sound's property is much better than before with less gas wasting. The researchers discussed four different typical modulation models in comparing their effectiveness and obtained fairly good results. For a typical male's speech signal, comparing with half-flow modulation, gas utilization ration of this full modulation is enhanced from 5% to 51.5%, for a sinusoidal was sound, the ratio keep in a maximum 60% in different modulation-rate, SNR of the sound generating is enhanced over 15 dB.