中频噪声mid-frequency noise
参考答案：
主要噪声成分的频率为500～1000Hz的噪声。
Helen had to shout ________ above the sound of the music. [ ]
A. making herself hear
B. to make herself hear
C. making herself heard
D. to make herself heard
蜘蛛痣的特征应除外( )。
A．呈辐射状B．压其中心部该痣可消失C．妊娠妇女多见D．下肢及腹部少见E．是一种特殊皮疹
