A low-pass filter is an electronic filter that passes low-frequency signals and attenuates (reduces the amplitude of) signals with frequencies higher than the cutoff frequency. T It is sometimes called a high-cut filter, or treble cut filter when used in audio applications. A low-pass filter is the opposite of a high-pass filter. 

Sound above the cutoff frequency is not eliminated but increasingly attenuated as the frequency rises further above the cutoff. The steepness of the attenuation is set by the rolloff value. For example, with a rolloff of 6 dB per octave, the sound decreases by 6 dB for each octave above the cutoff frequency (an octave above is double the frequency). 

Low-pass filter controls 

The only control for the low pass filter is its cutoff frequency. This varies from 0Hz to (Sampling rate)/2.