sound barrier

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sound barrier

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sound barrier (countable and uncountable, plural sound barriers)

1. (uncountable) Sonic barrier, the sudden increase in drag (resistance) and other effects experienced by moving objects when their speed approaches that of sound or becomes supersonic (which used to be considered a barrier to higher speeds).
2. (countable) A noise barrier, a structure beside a highway designed to reduce the noise of traffic.
   • 2021 October 6, Howard Johnston, “Regional News: Anglia”, in RAIL, number 941, page 29:

     St Ives: The guided busway on the old railway alignment to Cambridge has just passed its tenth anniversary. Railfuture has noted its down-at-heel physical appearance, with dirty concrete beams, damaged sound barriers, and unmanaged vegetation.

• speed of sound