1. What is Low Pass Filter
A Low Pass Filter passes frequencies below its cutoff frequency and
attenuates frequencies above its cutoff frequency. This effect can
therefore be used to reduce high pitched noise.
In other words, low-frequency signals go through much easier and with
less resistance and high-frequency signals have a much harder getting
through, which is why it's a low pass filter.
Low pass filters can be constructed using resistors with either capacitors
or inductors. A low pass filter composed of a resistor and a capacitor is
called a low pass RC filter. And a low pass filter with a resistor and an
inductor is called a low pass RL filter.
The cutoff frequency (sometimes also called corner frequency) defines
the point at which the audio is reduced by 3 dB. Thus there will also be a
small and decreasing amount of attenuation just below the cutoff
frequency as in the following image.