In the early Imperial age Roman unroofed theatres were endowed with velaria. Velaria were awnings made of sailcloth, in either canvas, linen or cotton, attached to spokes of rope that could be extended or retracted with ropes and pulleys over the cavea. Their main purpose was to provide shade for the spectators who watched the show in blistering sun and heat. The aim of this paper is to understand if velaria, beside their primary function, could affect the acoustics of the theatres. A specific study was carried out with the use of a commercial software for the prediction of room-acoustics characteristics of halls. Actually, numerical simulations were aided by acoustic measurements performed in two existing theatres, namely the "Teatro Grande" in Pompeii and the "Teatro Romano" in Benevento as they are in the present state. Both theatres are used rather regularly for public shows including music of various genres and drama. Like other ancient theatres not in a good state of conservation both theatres are deficient of natural reverberation because of the lack of structural elements important for this acoustic feature. To overcome inherent drawbacks electroacoustic means are used. However, there are instances where these remedial measures are not appropriate. The results of this study show that the use of suitable awnings can improve the reverberation in these venues. (C) 2015 Published by Elsevier B.V.