Low-pass filter

related topics
{system, computer, user}
{math, energy, light}
{math, number, function}
{rate, high, increase}

A low-pass filter is a filter that passes low-frequency signals but attenuates (reduces the amplitude of) signals with frequencies higher than the cutoff frequency. The actual amount of attenuation for each frequency varies from filter to filter. 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, and a band-pass filter is a combination of a low-pass and a high-pass.

Low-pass filters exist in many different forms, including electronic circuits (such as a hiss filter used in audio), digital filters for smoothing sets of data, acoustic barriers, blurring of images, and so on. The moving average operation used in fields such as finance is a particular kind of low-pass filter, and can be analyzed with the same signal processing techniques as are used for other low-pass filters. Low-pass filters provide a smoother form of a signal, removing the short-term fluctuations, and leaving the longer-term trend.

Contents

Examples of low-pass filters

Acoustic

A stiff physical barrier tends to reflect higher sound frequencies, and so acts as a low-pass filter for transmitting sound. When music is playing in another room, the low notes are easily heard, while the high notes are attenuated.

Electronic

In an electronic low-pass RC filter for voltage signals, high frequencies contained in the input signal are attenuated but the filter has little attenuation below its cutoff frequency which is determined by its RC time constant.

Full article ▸

related documents
Motion compensation
Shannon–Hartley theorem
Multivibrator
PIN diode
System call
Intel i860
Qt (toolkit)
Integrated development environment
Multiplexer
Balanced line
Non-return-to-zero
Disk partitioning
Decca Navigator System
Slackware
Carbon (API)
HP-UX
LaserWriter
ACIS
Fractal compression
Zener diode
Portable Executable
MX record
Forward error correction
MMIX
X86 memory segmentation
FLOPS
Exokernel
IS-IS
Shareaza
Network File System (protocol)