Development of Optophone with No Diaphragm and Application to Sound Measurement in Jet Flow

Figure 25

Frequency spectra of speaker sound in air jet flow. (a) 𝑀=0, (b) 𝑀=0.1, (c) 𝑀=0.25, (d) 𝑀=0.5.

(a)

(b)

(c)

(d)