Tutorial 2: Delay Based Effects

Tutorial 2: Delay Based Effects

In this section, we define a function to create echo effect on input audio. Echo can be modeled as attenuated, delayed copies of the original signal added to itself. Here, it can be seen as an FIR filtering operation. The FIR filter we constructed is of form [1, delayed_sec*Fs-1, a], where delayed_sec is the number of seconds for the echo to arrive and a: 0<a<=1.

We can also make the amount of delay a function of time to make more interesting effects, such as flanger. The following function implements the flanger effect using a triangular function for time-varying delay, shown in the figure below..

Source code and test audio file: tutorial2

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Dynamic Range Compression and Noise

This post accompanies our presentation “Dynamic Range Compression of Sound Mixtures” at the 2020 Acoustical Society of America meeting. Complete details are available in the paper preprint “Modeling the effects of dynamic range compression on signals in noise.”

Nearly every modern hearing aid uses an algorithm called dynamic range compression (DRC), which automatically adjusts the amplification of the hearing aid to make quiet sounds louder and loud sounds quieter. Although compression is one of the most important features of hearing aids, it might also be one of the reasons that they work so poorly in noisy environments. Hearing researchers have long known that when DRC is applied to multiple sounds at once, it can cause distortion and make background noise worse. Our research team is applying signal processing theory to understand why compression works poorly in noise and exploring new strategies for controlling loudness in noisy environments.

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