Bela
Real-time, ultra-low-latency audio and sensor processing system for BeagleBone Black
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Audio/telephone-fiter

Telephone filter

This sketch demonstrates how to use the Biquad library to filter an audio signal. A low-pass and a high-pass Butterwoth filters are used at 2kHz and 800Hz respectively to recreate the so-called 'Telephone filter' effect by band-limitting the input signal, making it sound like if it was played through a small bandwith speaker.

Both biquad filters are applied in series to a mono sum of the input signal creating a bandpass filter.

To learn more about Biquad filters and how to use the Biquad library, make sure to check Nigel Redmon's fantastic blog: https://www.earlevel.com/main/category/digital-audio/filters/iir-filters/biquads/