簡介

　　半導(dǎo)體自適應(yīng)定向傳聲器（ADM）算法是一二麥克風(fēng)處理方案助聽器。它的目的是自動減少源于后面或從配戴助聽器的一側(cè)不影響聲音前面。該算法實(shí)現(xiàn)了連續(xù)調(diào)整麥克風(fēng)極性圖案中的空白最小化ADM輸出端的噪聲電平（見圖1）。所需信號與噪聲完全基于到達(dá)方向的尊重致助聽器。前半球的聲音是通過無衰減，而聲音從后面來半球被認(rèn)為是噪音和減少。這個(gè)傳聲器極性圖案中零的角位置在90到180度范圍內(nèi)連續(xù)可變0度代表前面。

　　The location of the null in the microphone pattern is influenced by the nature of the acoustic signals （i.e.， spectral content and direction of arrival） as well as the acoustical characteristics of the room. The ADM algorithm steers a single， broadband null to a location that minimizes the output noise power. If a specific noise signal has frequency components that are dominant， they will have a larger influence on the null location than a weaker signal at a different location. In addition， the position of the null is affected by acoustic reflections. The presence of an acoustic reflection may cause a noise source to appear as if it originates at a location other than the source location. In this case， the ADM algorithm will choose a compromise null location that minimizes the level of noise at the ADM output. Figure 2 shows a screen shot of the Interactive Data Sheet （IDS） with the Adaptive Directional Microphone front end mode selected. Figure 3 shows IDS with ADM mode disabled.

　　The ADM as it was implemented on Inspiria Ultimate， the GA3285， also has an Auto mode. In this mode， when the ambient sound level is above a threshold of approximately 55dBSPL and the polar pattern has adapted to something other than omni-directional， then the adaptive polar pattern is enabled. If the polar pattern adapts to omni-directional， then the algorithm will switch to single microphone， omni-directional mode to reduce current consumption.