Jerusalem Talmud Rosh Hashanah 3:7

משנה: הַתּוֹקֵעַ לְתוֹךְ הַבּוֹר אוֹ לְתוֹךְ הַדּוּת אוֹ לְתוֹךְ הַפִּיטָּס אִם קוֹל שׁוֹפָר שָׁמַע יָצָא. וְאִם קוֹל הֲבָרָה שָׁמַע לֹא יָצָא. וְכֵן מִי שֶׁהָיָה עוֹבֵר אֲחוֹרֵי בֵית הַכְּנֶסֶת אוֹ שֶׁהָיָה בֵיתוֹ סָמוּךְ לְבֵית הַכְּנֶסֶת וְשָׁמַע קוֹל שׁוֹפָר אוֹ קוֹל מְגִילָּה אִם כִּוֵּין לִבּוֹ יָצָא. וְאִם לָאו לֹא יָצָא. אַף עַל פִּי שֶׁזֶּה שָׁמַע וְזֶה שָׁמַע זֶה כִּוֵּין לִבּוֹ וְזֶה לֹא כִּוֵּין לִבּוֹ: MISHNAH: If somebody blows into a cistern, or into a cellar, or into a barrel⁹⁶Greek πίθος., if he heard the sound of the shofar he fulfilled his obligation, if he heard the sound of the echo he did not fulfill his obligation. Similarly⁹⁷The two cases are not quite comparable. In the first case, two people hear similar sounds, one the original and the other the echo. In the second case both hear the same sound, but one intended to fulfill his religious obligation and the other did not., if somebody was passing by a synagogue or his house was near the synagogue and he heard the sound of the shofar or the reading of the Esther scroll, if he listened purposefully he fulfilled his obligation, otherwise he did not fulfill his obligation. Even though both heard, one listened purposefully, but the other did not listen purposefully.

הלכה: אָמַר רִבִּי יוֹסִִֵי בֶּן חֲנִינָה. לֹא אָמַר אֶלָּא וְכֵן מִי שֶׁהָיָה עוֹבֵר. הָא אִם עָמַד חֲזָקָה כִּיוֵּין. נָתַן שׁוֹפָר בְּתוֹךְ שׁוֹפָר (נֹאמַר) [וְתָקַע]. אִם קוֹל הַפְּנִימִי שָׁמַע יָצָא. אִם קוֹל חִיצוֹן שָׁמַע לֹא יָצָא. רִבִּי אֲבִינָּא בָעֵי. הֲפָכוֹ מָהוּ. נִישְׁמְעִינָהּ מִן הָדָא. גְּרָדוֹ מִבִּפְנִים פָּסוּל. מִבַּחוּץ כָּשֵׁר. לֹא אָמַר אֶלָּא גְרָדוֹ. הָא אִם הֲפָכוֹ פָסוּל. מַה בֵין זֶה לַזֶה. זֶה בִיטֵּל חֲלָלוֹ וְזֶה לֹא בִיטֵּל חֲלָלוֹ. HALAKHAH: Rebbi Yose ben Ḥanina said, it only said “somebody was passing by.” Therefore if he stood still, the presumption is that he listened purposefully⁹⁸The Babli, 29a, has a problem whether the person who blew the ṣhofar intended to benefit also the casual listener.. ⁹⁹Babli 27b, Tosephta 2:4.“If he put one shofar inside another shofar(,we shall say) [and blew]¹⁰⁰The corrector’s text in brackets follows the Babli and the Tosephta., if one heard the sound of the inner one, he has fulfilled his obligation, if one heard the sound of the outer one, he has not fulfilled his obligation.” Rebbi Abinna asked, what if he turned it inside out? Let us hear from the following¹⁰¹In the Babli sources (Note 99) the reading is: “inside or outside it is qualified.” The Yerushalmi text should not be adapted to the Babli since roughing the surface inside changed the sound chamber.: “If he scratched it inside it is disqualified, outside it is qualified.” He only said, he scratched; therefore if he turned it inside out it is disqualified. What is the difference between the two? One eliminated the inner space, the other did not eliminate the inner space.