Hearing aids with automatic signal processing circuitry, Automatic Signal Processing( ASP), are designed to improve speech reproduction in the presence of strong ambient noise. ASP technology is superior to classic hearing aids without automatic signal processing when background noise severely affects listening conditions.
With automatic signal processing, not only is the gain controlled as a function of the input signal, but also the frequency response. While traditional automatic signal processing uses automatic gain control( AGC) or compression techniques to attenuate high-levelsignals, this technique, called fixed frequency response (FFR), has no dynamic effect on frequency response. The situation is different with the level-dependent technique, Level Dependent Frequency Response (LDFR). Thus, LDFR reduces the gain of low frequencies with a high input level.
The second circuit reduces high input levels from high frequencies. The overall response of the two channels, with their programmable compressors, can be controlled according to the input signal, allowing the user to achieve optimal speech reproduction. Their characteristics can be automatically adjusted to the input signal over a wide frequency and level range.