sound amplifier meaning in English

扩音机
声频放大器
音频放大器

In addition , the author puts forward that the eggs could be recognized based on the difference in the frequencies of their prompted sounds . because the eggs " prompted sounds are lied on low frequency bands , the microphone and sound amplifier that have excellent duration response should be used . the output signal from the sound amplifier is transferred to data signal by a / d card before it is put into computer
蛋品激励出的声音主要集中在低频段，因此选择在低频段有好的频率响应特性的麦克风和放大电路；放大输出信号通过a / d采集板变换成相应的电压数值信号送入计算机，对离散的信号数据进行傅立叶变换得到它的频谱图和各频段能量分布图；而后将能量分布特征数据作为神经网络的输入值，这样，好蛋和破损蛋的模型就建立起来。