There are rules for hearing the sound of the shofar, and those rules can be divided into two groups: rules for how the sound is made, and rules for how the sound is heard.
The rules for the former, at first glance, seem straightforward: Use the right kind of horn. Don’t put gold around the shofar’s mouthpiece. Don’t use a broken shofar, even if you glued it back together. Make sure the blasts are the right duration, and don’t blow the shofar at the same time as you blow another instrument. Don’t mutilate the shofar, don’t turn the shofar inside out — and in the event that you find yourself blowing a shofar inserted inside of another shofar, make sure it is the sound of the inner one that people hear.
We’ve already discussed some of these rules, and a few are self-explanatory. The rule about blowing the shofar alone might be the most interesting of the bunch, since it relies on a theory — recently elaborated by Lynn Kaye in her book about time in the Babylonian Talmud — that simultaneity is divine. For the rabbis of the Talmud, God alone can say two things at once, and hearing two things at once is also an exclusively divine trait.
So there are rules for the blower. But there are rules for the listener and chief among them is that one must hear the sound of the shofar and not an echo of that sound. This might come up if, say, you were hearing the sound of the shofar from the bottom of a pit or cistern.
Figuring out the reason for this prohibition is harder than it looks. A modern might say that we want listeners to perceive the oscillations in the air before they have had a chance to bounce off anything; framed this way, the rules for shofar sound a little like the rules for a kosher mikveh, which require a certain amount of water that has fallen straight from the sky without humans interfering with it along the way. But this just isn’t how sound works. Unless you are hearing the shofar in an anechoic chamber, the sound you hear will always be a mixture of the sound that went straight to your ears and the sound that bounced around the room. In the podcasting business we call this amalgam of echoes reverb.
But the ancient rabbis didn’t know about reverb, and their understanding of echoes and sound itself was likely quite different from our own. Exactly how sound propagated was unknown until the early modern period, when — ironically — echoes became an important tool to understand the mechanism of sound transmission. This is to say that a person curious about the Talmud’s concern with echoes may need to begin by studying the history and mythology of echoes. I leave the invitation open — if you figure something out, please let me know!
What confounds all of this, however, is that none of this rigmarole about blowing and hearing the shofar seems to be in the service of engendering the experience of any specific sound. In fact, says Rabban Gamliel, “all shofar sounds are fit” — that is, we care about the procedure for making and hearing that sound, but not the sound itself. What, then, are all these rules trying to preserve — and what should we make of the disdain for echoes and deformed horns?
Read all of Rosh Hashanah 27 on Sefaria.