An Audio filter can be defined as a type of filter used for processing sound signals. In its simplest form, an audio filter is typically designed to pass some more frequency regions by strengthening one while significantly weakening others. In a general way, the term audio filter can be defined as anything that alters the characteristic of an audio signal. Filters are actually electronic circuits that perform signal processing function.

Purpose of use:
Basically audio filter serves three purposes:

• Limits band width of the audio response and restrict the transmitted bandwidth to less than 4KHz.
• Helps preserve suppression specifications of sideband.
• Decreases high-order audio distortion elements.

Types of Audio Filters
Many different types of audio filter are available in the market for different applications. Filters can be classified into various types according to their usage.

Classification of Audio Filters by Technology:

• Analog filter
• Digital filter
• Passive filter
• Active filter
• Linear filter
• Non-linear filter

Classification of Audio Filters by transfer function:

• Low-pass filter
• High-pass filter
• Band-pass filter
• Band-stop filter

Maintenance of Audio Filters
Proper care must be taken for audio filters to get better sound quality. To achieve this, filters should be used on regular interval depending on driving conditions. A filter care service kit containing a filter cleaner is generally used for cleaning of audio filters.

Application of Audio Filters
There are various applications of audio filters. Some of the areas where audio filters find application are:

• Graphic equalizers
• Synthesizers
• Sound effects
• CD players
• Virtual reality systems