A fastening element for assembling a sound-absorbent and/or sound-insulating barrier along a communication pathway, the barrier comprising a plurality of sound-absorbent and/or sound insulating panels frontally fixed to an upright by the fastening element, wherein the upright comprises a coupling portion which is conformed as an upright bar, wherein a sound-absorbent and/or sound-insulating panel (5, 6) of the plurality of sound-absorbent and/or sound-insulating panels comprises a lateral wall (50, 60) which is provided above or below it with a projection or a recess, wherein the fastening element is to be constrained between the upright and the sound-absorbent and/or sound-insulating panel (5, 6) for fixing the panel (5,6) frontally to the upright; characterised in that the fastening element comprises: a plate which affords a through-opening, which through-opening originates from a first flank of the plate and an anchoring portion which is C-shaped and originates from a second flank of the plate, and an abutting portion which originates from a flank of the plate which is opposite the second flank of the plate, wherein the through-opening is conformed for receiving the coupling portion of the upright so that the fastening element is constrained in horizontal position of the plate to the upright through the opening afforded in the plate which receives the coupling portion of the upright; wherein the anchoring portion is dimensioned such that when the fastening element and the sound-absorbent and/or sound-insulating panel (5, 6) are assembled, the C-shaped anchoring portion internally contains the projection or is contained internally of the recess of the lateral wall (50,60) of the sound-absorbent and/or sound-insulating panel (5, 6) so that the sound-absorbent and/or sound-insulating panel (5, 6) is fixed to the upright by means of the anchoring portion of the fastening element; and wherein the abutting portion is conformed for abutting the coupling portion of the upright when the fastening element is constrained to the upright. a plate which affords a through-opening, which through-opening originates from a first flank of the plate and an anchoring portion which is C-shaped and originates from a second flank of the plate, and an abutting portion which originates from a flank of the plate which is opposite the second flank of the plate, wherein the through-opening is conformed for receiving the coupling portion of the upright so that the fastening element is constrained in horizontal position of the plate to the upright through the opening afforded in the plate which receives the coupling portion of the upright; wherein the anchoring portion is dimensioned such that when the fastening element and the sound-absorbent and/or sound-insulating panel (5, 6) are assembled, the C-shaped anchoring portion internally contains the projection or is contained internally of the recess of the lateral wall (50,60) of the sound-absorbent and/or sound-insulating panel (5, 6) so that the sound-absorbent and/or sound-insulating panel (5, 6) is fixed to the upright by means of the anchoring portion of the fastening element; and wherein the abutting portion is conformed for abutting the coupling portion of the upright when the fastening element is constrained to the upright.