a device that allows signals within a certain range of frequencies to pass through and stops signals outside that range

It is necessary to filter the incoming radiation to eliminate false signals from common household infrared emitters such as remote control devices, which can be achieved using a simple bandpass filter. 有必要对传入的辐射进行过滤，以消除来自遥控装置等普通家用红外发射器的错误信号，这可以通过使用简单的带通滤波器来实现。

The LED spectrum of the light can be narrowed by installing a band-pass filter.

to use a special device to allow only signals within a certain range of frequencies to pass through

Signals were amplified, band-pass filtered, and digitally stored for off-line analysis. 信号经过放大、带通滤波和数字存储后进行离线分析。

A bandpass filtered recording was used.