Speech Variable Processing
Speech Variable Processing is a fast-acting technology that measures and amplifies sound. By mimicking how the ear analyzes and adjusts sounds, Speech Variable Processing helps keep sound natural and speech clear.
Speed is Key to Accuracy
The inner ear structure - called the cochlea - is key to perceiving sound volume and clarity. Not only does the cochlea "receive" sound, it amplifies sound when it is healthy. A processing system that wants to replicate this behavior authentically has to react just as fast.
Speech Variable Processing is a Wide Dynamic Range Compression (WDRC) system specifically designed for very fast sound processing. It analyzes an incoming signal and adjusts the gain, or amplification, thousands of times per second. This ability to quickly identify a sound and apply amplification (the attack time) and then to change the gain when the sound changes (the release time) is what allows Speech Variable Processing to enhance speech intelligibility and create a natural sound.
A good example of how quickly sounds change is when you say the words, “Everyday Sounds Better.” The final “s” in “Sounds” is much quieter than the hard “B” in “Better.”
A healthy cochlea automatically detects and adjusts for this. Speech Variable Processing also analyzes this sound change in milliseconds in order to provide proportional amplification.
Systems with fast attack and slow release times (orange) don’t react quickly enough to changes in sound pressure—they apply too little amplification on the soft “s” sound and too much on the hard “B” sound. With its very fast attack and release times, Speech Variable Processing (blue) accurately measures and compensates for sudden changes in sound—the “s” and “B” sounds each get the appropriate amount of amplification to sound natural.
Clarity Requires Frequency Contrast
If speed is the key to accuracy, then contrast is the key to clarity. Sounds have different frequencies that help form speech. Hearing the contrast between frequencies is what gives clarity in speech.
A healthy cochlea maintains this contrast as it amplifies sounds, but with a sensorineural hearing loss, the cochlea isn’t able to amplify as well at different frequencies. Speech Variable Processing helps overcome this loss of contrast by measuring and applying gain to the entire wideband acoustic signal.
Other processing approaches split the incoming signal into separate channels, apply gain, then put the channels back together. This creates a “summing” effect—all the amplification is applied equally and the result is a loss of contrast.
Speech Variable Processing, on the other hand, measures and adjusts frequency regions individually. By applying gain to the appropriate ranges, this system preserves the frequency contrast of the natural sound.
Illustration of the frequency contrast for the vowel sound / e /. Speech Variable Processing (blue) closely matches the peak-to-valley contrast of the original signal, while the multichannel approach (orange) flattens the signal. Maintaining the contrast is important to experience clarity in speech.