We study the evolution of the acoustic properties of porous polymer materials in the glass transition temperature domain. First, we study the cross-linked 2-ethylhexyl acrylate (EHA) - 2-ethylhexyl methacrylate (EHMA) non-porous matrices at various compositions and, consequently, various glass transition temperatures. Based on the frequency-temperature equivalence principle, we build master curves in order to determine the bulk (K-0) and shear (G(0)) moduli corresponding to ultrasonic frequencies (about 300 kHz). Next, we synthesize some porous samples of these matrices using the emulsiontemplated polymerization approach usually known as polyHIPE (for polymerized High Internal Phase Emulsion). We measure the longitudinal sound speed C-L. for different matrix compositions (at room temperature) or at different temperatures (for the same sample composition). As expected, we show that the sound speed decreases with increasing K-0/G(0) ratio, i.e. as matrices become softer, which is either due to an increase of EHA content or to an increase of the temperature. This demonstrates how composition and temperature may be used to tune the sound speed in porous polymers. We show that the theoretical predictions using a low-frequency multiple scattering model leads to underestimated values of the sound speed, especially for soft matrix. We attribute this discrepancy to the difference in mechanical properties of the polymer matrix between non porous and porous samples. (C) 2018 Elsevier Ltd. All rights reserved.