Bentching When You Can’t Hear Yourself Speak
There is a halachic requirement l’hashmiah l’aznav (to hear yourself speak) while performing certain mitzvos, such as davening or bentching (reciting an after-blessing). This means actually saying each word audibly. This practice can be difficult under very noisy circumstances—such as attempting to recite birchas hamazon (Grace After Meals) at a wedding while music is blasting so loudly that it’s impossible to hear your friend even if he’s shouting!
(Whether the extreme volume of the music at weddings is halachically acceptable is another discussion, since many scientific studies warn of the danger posed by repeated exposure to such high-decibel sound.)
An eitzah (suggestion), if you are in such a situation, is to close one ear and perhaps raise your voice higher than normally required, so as to hear the words of your own bentching.
חסל״א הובא בכה״ח סב, ז. מנחת יהודה הו״ד בשפ״ח שמות ח, ח. הליכות שלמה כב, ד. וראה העמק שאלה שאילתות ואתחנן קמג שהוכיח בדעת השאילתות ובה״ג שאינו יוצא בכה״ג. וראה קובץ משנת יוסף גל׳ יג ס״נ.