PTA-A PTA-D SRT-A SRT PTA A-D Gap 純音聽力上升檢查法 純音聽力下降檢查法 語音閾值上升檢查法 語音與純音聽閾值的差異 上升與下降檢查法聽閾值的差異 Pure tone thresholds were obtained by ascending procedure Pure tone thresholds were obtained by descending procedure Speech recognition thresholds were obtained by descending procedure The discrepancy between ascending and descending procedure