DSP Audio Effects Project

Audio equalization deals with the tuning of different frequency bands of an audio signal. Using linear filters, the gain of frequency components can be changed to achieve the desired sound. The simplest approach is to use low pass, band pass, and high pass filters to control the different frequency bands. The lowest frequencies are known as the bass, and this typically refers to frequencies around 400 Hz and below. The highest frequencies, known as treble, typically are frequencies above 4 KHz. The frequencies in between the treble and bass is known as the mid range. These frequency ranges can be broken up into more partitions, but for our equalizer we stuck with the basic three ranges. 

 

Our implementation of an audio equalizer consisted of a low pass filter, with a cutoff frequency of 400 Hz, a band pass filter that with cutoff frequencies of 400 Hz and 4000 Hz, and a high pass filter with a cutoff of 4000 Hz. With these three filters combined, we can isolate a specific frequency range of an audio signal.

 

Another implementation that we applied consisted of shelving and peaking filters. Low and high pass filters are useful in cutting frequencies beyond a desired cutoff, but shelving filters can evenly cut or boost frequencies on either side of the cutoff frequency. Peaking filters work similarly to shelving but are applied between two cutoff frequencies, just as a band pass filter would. 

 

Equalizers are typically used to alter responses of microphones, speakers, and adjust for room acoustics. Also used in music production to bring out a certain sound for a specific instrument or voice in a full mix that includes various instruments that span a wide range of frequencies.