Page 267 - The Master Handbook Of Acoustics
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242 CHAPTER TEN
FIGURE 10-7
Close-up of the levitated cork chips of Fig. 10-6. If the cork chips are spaced about
1 ⁄2 inch, the frequency of the sounds emitted by the Galton Whistle is about 30 kHz.
A similar situation prevails in an air-conditioning duct. A sound
wave (noise) traveling in the duct suddenly encounters the large open
space of the room. This discontinuity (impedance mismatch) reflects a
significant portion of the sound (fan noise, etc.) back toward the
