What is the purpose of a filter in audio processing?

The purpose of a filter in audio processing is to remove specific sound frequencies. Filters are essential tools used to manipulate sound by allowing some frequencies to pass through while attenuating or eliminating others. This capability is crucial for various applications, such as reducing unwanted noise, shaping the tonal quality of audio, or isolating particular sounds or instruments within a mix. For instance, a low-pass filter allows low frequencies to pass while cutting off higher frequencies, which can help eliminate hiss or other high-frequency noises.

When it comes to the other options, enhancing reverb is typically achieved through effects processing rather than directly with filters. Amplifying all frequency components does not align with the selective functionality of filters, which strategically allow or block certain frequencies. Adjusting the starting sound value refers to modifying volume or gain rather than frequency manipulation, which is separate from the primary role of filters in audio processing.