Why are these Problems Difficult to Solve?
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While there have been many attempts to address the previously articulated problems, they are far more difficult and challenging than they first appear. What works in the lab, typically doesn't function well in the real world.

As a result, most of the patents that have been filed, don't work, and there are not many products that can claim to address these problems.

Low Cost Compression Limiters

Consumer electronics products need very cost effective solutions. To date, compression limiters have been the only viable low-cost approach to limiting the maximum volume produced by these products. Sony, Magnavox, and many cable boxes limit their maximum sound output by using compression limiters. This results in flattening the sound above a given threshold, causing sounds to become flat and unrealistic.

Another problem with compression limiters is that in order to avoid distortion at lower frequencies, slow attack & releases are used that can result in clipping or under amplification of the signal.

Prior-Art High Quality Compander Solutions

High quality companders are used in studios, audio workstations, and other professional environments. Typically they require considerable technical expertise to use, as well as a fair amount of trial and error experimentation to minimize distortion and provide the desired sound. To minimize distortion, multi-band, computationally intensive, and expensive designs are often used. When multiple channels are being processed, traditional designs may suffer from interchannel modulation distortion.

Studio engineers typically use these companders to convert the wide dynamic range of the sound track of a movie to a greatly reduced dynamic range when creating a DVD version of the movie. While this results in a product that can be heard on a stereo TV with poor built-in speakers in a small room, it prevents a home theater from reproducing the original theatrical viewing experience.

Prior-Art Noise Compensators

Compensating for noise requires accurately measuring environmental noise that is constantly changing. If a microphone is used to detect both the environmental noise and sound that is being generated, this can easily result in a gain chase problem. Because the noise is constantly changing, other prior-art has attempted to use very long response times or non-acoustic methods in order to obtain a stable response.