Based on siren incentive system

the energy transform relationship between unsteady flow fluctuation velocity brought by siren actuator and acoustic particle velocity got by the two-microphone technique was derived. And the effect of incentive intensity

frequency

Mach number and the sensor spacing on the acoustic particle velocity was studied through the aeroacoustic characteristic experiment

verifying the theoretical model. The results are as follows: acoustic particle velocity can't be fully converted by unsteady flow fluctuation velocity

the transform relationship between velocities mentioned above is related to Mach number. Under incompressible condition

Mach number less than 0.3

the energy transform factor is proportional to the square of Mach number

and the larger Mach number means

the larger energy transform factor

and the higher conversion efficiency of unsteady flow to acoustic energy.