Burkhard M D, Sachs R M
J Speech Hear Res. 1977 Dec;20(4):799-807. doi: 10.1044/jshr.2004.799.
It is known that sound pressure, measured in couplers via a probe-tube microphone, often shows a pressure vs frequency response that drops sharply at a single frequency. In this study sound pressure was theoretically determined at various locations within a hard-walled cylindrical cavity, driven by a constant-volume velocity source with circular symmetry. At each location in the volume, a transfer impedance was defined as the ratio of pressure to inlet-volume velocity. In the region around the inlet, the transfer impedance passes through zero as it changes from negative to positive reactance with increasing frequency. Two hard-walled cavity examples were examined in detail (1) the main cavity of a 2-cm3 HA-2 coupler, and (2) a cavity having dimensions approximately equal to the occluded ear canal between an ear-mold tip and the eardrum. Contours of constant minimum sound pressure vs frequency are given for these two cylindrical volumes with experimental verification. Implications for probe microphone calibration and measurement of sound pressure in ears are discussed.
众所周知，通过探管传声器在耦合器中测量的声压，其压力与频率的响应通常在单一频率处急剧下降。在本研究中，理论上确定了由具有圆对称性的定容速度源驱动的硬壁圆柱腔内不同位置的声压。在该体积内的每个位置，将传输阻抗定义为压力与入口体积速度之比。在入口周围区域，随着频率增加，传输阻抗从负电抗变为正电抗时会经过零点。详细研究了两个硬壁腔实例：（1）一个2立方厘米HA-2耦合器的主腔，以及（2）一个尺寸大致等于耳模尖端与鼓膜之间封闭耳道的腔。给出了这两个圆柱体积的恒定最小声压与频率的等高线，并进行了实验验证。讨论了对探头传声器校准和耳内声压测量的影响。
