[a:0]aselect=n=2:e=1+between(t,t0,t1)+between(t,t2,t3)+...[aud_silent_in][aud_sounded_in];
[aud_silent_in]atempo=2.0,atempo=2.0,atempo=1.25,afifo[aud_silent_out];
[aud_sounded_in]atempo=2.0,afifo[aud_sounded_out];
[aud_silent_out][aud_sounded_out]concat=n=2:v=0:a=2[aud_out]