Please first read it.
Franz Kafka, “The Silence of the Sirens”
Proof that inadequate, even childish measures, may serve to rescue one from peril.
To protect himself from the Sirens Odysseus stopped his ears with wax and had himself bound to the mast of his ship. Naturally any and every traveller before him could have done the same, except those whom the Sirens allured even from a great distance; but it was known to all the world that such things were of no help whatever. The song of the Sirens could pierce through everything, and the longing of those they seduced would have broken far stronger bonds than chains and masts. But Odysseus did not think of that, although he had probably heard of it. He trusted absolutely to his handful of wax and his fathom of chain, and in innocent elation over his little stratagem sailed out to meet the Sirens.
Now the Sirens have a still more fatal weapon than their song, namely their silence.
And though admittedly such a thing has never happened, still it is conceivable that someone might possibly have escaped from their singing; but from their silence certainly never. Against the feeling of having triumphed over them by one's own strength, and the consequent exaltation that bears down everything before it, no earthly powers could have remained intact. And when Odysseus approached them the potent songstresses actually did not sing, whether because they thought that this enemy could be vanquished only by their silence, or because of the look of bliss on the face of Odysseus, who was thinking of nothing but his wax and his chains, made them forget their singing. But Odysseus, if one may so express it, did not hear their silence; he thought they were singing and that he alone did not hear them. For a fleeting moment he saw their throats rising and falling, their breasts lifting, their eyes filled with tears, their lips half-parted, but believed that these were accompaniments to the airs which died unheard around him. Soon, however, all this faded from his sight as he fixed his gaze on the distance, the Sirens literally vanished before his resolution, and at the very moment when they were nearest to him he knew of them no longer.But they--lovelier than ever--stretched their necks and turned, let their cold hair flutter free in the wind, and forgetting everything clung with their claws to the rocks. They no longer had any desire to allure; all that they wanted was to hold as long as they could the radiance that fell from Odysseus' great eyes. If the Sirens had possessed consciousness they would have been annihilated at that moment. But they remained as they had been; all that had happened was that Odysseus had escaped them.
My first question is not as to why the sirens didn't sing. The possible answers to that are given by Kafka himself as you can read. But what I really want to know is how could their "not singing" possibly be a more dangerous weapon than singing, in the first place? Knowing that, for a given fact, that all attempts blocking the human ear canal prove futile against their enchanting voices anyhow.
Are they, the sirens, not aware of that fact?
My second question: why in his version of the Odyssey did Kafka made Odysseus' put wax in his own ears instead of his crew's, who, the latter, shackled him to the ship's mast? Was he explicitly mistaken here, or did he implicitly alter the story?