FIG. 2.

Cartoon of the experimental setup for pressure measurements in simple tubes. In (A), the sound source (Audax) was placed in a long anechoic tube and the pressure near the source was measured with a probe-tube microphone (ER7C). In such conditions, the pressure measured with the ER7C approximates the emitted pressure (i.e., the initial outgoing going wave at the sound source). In (B), the sound source was inserted into a brass tube terminated with an OAE probe assembly (ER10X). The total pressure generated by the sound source was recorded with the ER10X microphone and transformed to an estimate of emitted pressure using Eq. (2).