Principles behind Speech Guard

Speech Guard preserves signal fidelity and the important details of speech.

By fully preserving speech and spatial cues, and by greatly enhancing transparency, Speech Guard takes sound quality to even greater heights. Naturally, the more the amplified signal resembles the original speech signal, the better the listener’s perception will be.

 

The new principle of Floating Linear Gain in Speech Guard helps preserve the dynamic details of speech across environments, resulting in audible but, importantly natural speech sounds. Providing a clear and natural signal reduces listening effort and increases the listener’s ability to follow conversations. Floating Linear Gain in Speech Guard provides improved waveform fidelity, maximizes speech audibility and offers ultra fast and comfortable loudness (transient) protection.

When the sound is steady with minimal changes in loudness, the gain is linear and amplification slowly adapts to changes in the input level. For sounds which are too soft or too loud, Speech Guard responds rapidly with fast compression for an instant, to quickly return to an appropriate linear gain window. This assures that speech and spatial cues are amplified in a more natural and consistent way across different listening environments and this is the basic principle of Floating Linear Gain in Speech Guard.

Speech Guard in action

Participating in conversation requires an ability to follow speech over time. This means being able to focus on the individual speaking while ignoring competing sounds such as sudden loud sounds (transients) or stable background noise. Speech is dynamic; its loudness level changes over time. Loudness changes are important natural cues that make it easier to differentiate one voice from another thus making it easier to follow conversations.

This unprocessed speech envelope with a transient shows a waveform with a 6 dB modulation depth and no distortion in the signal. The transient is a short peak (50 ms) of 80 dB. With Floating Linear Gain in Speech Guard the output signal preserves the 6 dB modulation depth and the distortion-free quality.

The transient is kept audible at a loud but comfortable level, where it does not disturb or attract attention. The Floating Linear Gain in Speech Guard reacts so quickly when handling the transient that the ongoing signal is perceived as intact. With a conventional compression system the modulation depth is reduced and the envelope waveform is corrupted. When handling the transient the compressor attacks too slowly, making the transient very loud and annoying. It also releases too slowly, which makes the ensuing speech signal sound distorted and, in the worst case, inaudible.