The original Italian is "là dove 'l sol tace" and, according to Bianca Garavelli in her notes to Dante's Inferno, it refers to
il buio della «selva». L'immagine fonde i due sensi di vista e udito.
the darkness of the forest. The image merges the two senses of sight and hearing.
In the notes to the Inferno by Anna Maria Chiavacci Leonardi she explains the meaning of the expression "là dove 'l sol tace" in this way:
nella selva, dove regna l’oscurità totale. Il traslato dalla vista all’udito (’l sol tace), di origine virgiliana («tacitae per amica silentia lunae»: Aen. II 255), è una delle veloci metafore che Dante spesso chiude in un verbo e che danno forza al suo linguaggio (lo stesso traslato a V 28: d’ogne luce muto).
in the forest, where total darkness reigns. The switch from sight to hearing (’l sol tace), of Virgilian origin («tacitae per amica silentia lunae»: Aen. II 255), is one of the quick metaphors that Dante often closes in a verb and that give strength to his language (the same metaphorical use in V 28: d’ogne luce muto).
And in the notes by Maria Teresa Balbiano d’Aramengo you can find this explanation in reference to the "restless beast" (the She-wolf) that appears in your quotation:
Con il suo aspetto pauroso dà a Dante “tanto di gravezza”, tanto gli appesantisce l’anima, da scoraggiarlo nel suo tentativo di ascesa e ricacciarlo “dove il sol tace”: la lupa fa della mente umana una “mente cieca, che non sa vedere... che il numero” (cfr. Canz. “Doglia mi reca”); cieca ad ogni luce di bellezza e nobiltà, a tutto quello che non rende niente di concreto.
With its frightening aspect it gives to Dante "such heaviness", it weighs down his soul so much that it discourages him in his attempt to ascend and push him back "where the Sun is silent": the She-wolf makes the human mind a “blinded mind, that cannot see... that the sum" (cf. Dante's canzone “Doglia mi reca”); blinded to every light of beauty and nobility, to everything that brings in nothing concrete.
Alfredo Menetti also explains the following in his book Temi critici danteschi:
Sta di fatto che senza l'intervento dell'intelletto illuminato dalla grazia l'uomo ritornerebbe «là dove il sol tace».
It's a fact that without the intervention of the intellect illuminated by grace man would return to "where the Sun is silent".
In the book Cuori intelligenti. Mille anni di letteratura: dalle origini al Rinascimento by Claudio Giunta there is an explanation about the meaning of the verse "mi respingeva là dove 'l sol tace" ("drove me back to where the Sun is silent" in your translation) which says:
mi respingeva nella selva oscura, dove non penetra raggio di sole. Da notare la splendida sinestesia, che unisce un'impressione visiva (la
luce del Sole, qui assente) a una auditiva (il "silenzio" del Sole stesso, nell'oscurità della selva).
it drove me back to the dark forest, where no sunlight penetrates. Note the splendid synaesthesia, which combines a visual impression (the sunlight, absent here) to an auditory one (the "silence" of the Sun itself, in the darkness of the forest).
In the article “TOWARD ORDER AND TRANSCENDENCE: DANTE’S USE OF SYNAESTHESIA IN THE ‘DIVINE COMEDY’”, published in Romance Notes 21, no. 1 (1980) 111–16 by Kay Dickinson, the author explains that there are lots of instances of synaesthetic images in the Divine Comedy. In the words of Dickinson:
Dante's intense aliveness to the sights, sounds,
and other sensory aspects of his surroundings – be they those of Hell, Purgatory, or Paradise – as well as his endeavors to reach language's upper thresholds of expressivity, makes the appearance of synaesthesia in the Divine Comedy almost inevitable. And the poet's use of synaesthetic images seems to have, as this paper will attempt to demonstrate, a particular relationship to two aspects of the poem; namely, its emphasis on order and its movement toward transcendence.
The first synaesthetic image to be found in the Divine Comedy is precisely the one you quoted in your question, that is, the expression "where the Sun is silent":
[...] Dante speaks of the she-wolf driving him back to where the "sun is silent," gains its impact through the dominant role which light symbolism assumes in the poem. The sun itself is "a figuration of divine and intellectual light" – a symbol of God; consequently, Dante's rout to where the "sun is silent" points up the poet's lack of spiritual illumination at this stage in his journey. Further, since in the synaesthetic image of a sun devoid not only of visual but auditory – and, by extension, kinetic - attributes, there is presented
the diametrical opposite of the spiritually illuminated singing, circling "suns" appearing in Paradise, the profound extent of this spiritual
blindness is adeptly underlined. Indeed, the depiction of the sun as "silent" at this point in the Divine Comedy underscores the condition of the inhabitants of Hell: instead of reflecting the radiance of God as do the souls of the blessed, there is no interaction between them and Divinity – they are immersed in total moral and spiritual darkness.