וְחַנָּ֗ה הִ֚יא מְדַבֶּ֣רֶת עַל־לִבָּ֔הּ רַ֚ק שְׂפָתֶ֣יהָ נָּע֔וֹת וְקוֹלָ֖הּ לֹ֣א יִשָּׁמֵ֑עַ וַיַּחְשְׁבֶ֥הָ עֵלִ֖י לְשִׁכֹּרָֽה׃
原來哈拿是在心裡默默禱告,只有嘴唇在動,卻聽不見她的聲音,因此以利以為她喝醉了。
Mishneh Torah, Prayer and the Priestly Blessing
Modulation of the voice. The voice should not be raised during the recital of the Amidah prayer nor should it be offered [silently] in thought alone. The words should be pronounced with the lips, but softly, and yet be audible to the speaker's ears. The worshiper should not permit his voice to be heard by others, unless he is sick, or is unable to concentrate his attention without reading aloud. He may not, however, do so at public worship, so that the congregants shall not be disturbed by his loud praying.
Kitzur Shulchan Arukh
Take care to pray quietly so that only you yourself may hear what you are saying,18This law applies only to the Shemoneh Esrei. but someone standing next to you should not hear your voice, as Scripture says of Hannah: "Only her lips moved [but] her voice could not be heard."19I Samuel 1:13.