I just noticed there are multiple threads:

(gdb) thread apply all bt

Thread 7 (Thread 0xac9deb70 (LWP 14896)):
#0  0xb7fe2430 in __kernel_vsyscall ()
#1  0xb7434ba6 in poll () from /lib/tls/i686/cmov/libc.so.6
#2  0xb6c8ccc2 in ?? () from /usr/lib/libpulse.so.0
#3  0xb6c79e09 in pa_mainloop_poll () from /usr/lib/libpulse.so.0
#4  0xb6c7bc23 in pa_mainloop_iterate () from /usr/lib/libpulse.so.0
#5  0xb6c7bcf4 in pa_mainloop_run () from /usr/lib/libpulse.so.0
#6  0xb6c8cbc3 in ?? () from /usr/lib/libpulse.so.0
#7  0xb6c4fac2 in ?? () from /usr/lib/libpulsecommon-0.9.19.so
#8  0xb7e9580e in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#9  0xb74427ee in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 6 (Thread 0xb11e0b70 (LWP 14895)):
#0  0xb7fe2430 in __kernel_vsyscall ()
#1  0xb7434ba6 in poll () from /lib/tls/i686/cmov/libc.so.6
#2  0xb6c8ccc2 in ?? () from /usr/lib/libpulse.so.0
#3  0xb6c79e09 in pa_mainloop_poll () from /usr/lib/libpulse.so.0
#4  0xb6c7bc23 in pa_mainloop_iterate () from /usr/lib/libpulse.so.0
#5  0xb6c7bcf4 in pa_mainloop_run () from /usr/lib/libpulse.so.0
#6  0xb6c8cbc3 in ?? () from /usr/lib/libpulse.so.0
#7  0xb6c4fac2 in ?? () from /usr/lib/libpulsecommon-0.9.19.so
#8  0xb7e9580e in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#9  0xb74427ee in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 5 (Thread 0xb59e2b70 (LWP 14894)):
#0  0xb7fe2430 in __kernel_vsyscall ()
#1  0xb7434ba6 in poll () from /lib/tls/i686/cmov/libc.so.6
#2  0xb6c8ccc2 in ?? () from /usr/lib/libpulse.so.0
#3  0xb6c79e09 in pa_mainloop_poll () from /usr/lib/libpulse.so.0
#4  0xb6c7bc23 in pa_mainloop_iterate () from /usr/lib/libpulse.so.0
#5  0xb6c7bcf4 in pa_mainloop_run () from /usr/lib/libpulse.so.0
#6  0xb6c8cbc3 in ?? () from /usr/lib/libpulse.so.0
#7  0xb6c4fac2 in ?? () from /usr/lib/libpulsecommon-0.9.19.so
#8  0xb7e9580e in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#9  0xb74427ee in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 3 (Thread 0xb61fbb70 (LWP 14892)):
#0  0xb7fe2430 in __kernel_vsyscall ()
---Type <return> to continue, or q <return> to quit---
#1  0xb7434ba6 in poll () from /lib/tls/i686/cmov/libc.so.6
#2  0xb6d869b2 in ?? () from /usr/lib/gstreamer-0.10/libgstalsa.so
#3  0xb7e02895 in ?? () from /usr/lib/libgstreamer-0.10.so.0
#4  0xb7e041a7 in ?? () from /usr/lib/libgstreamer-0.10.so.0
#5  0xb7f7499f in ?? () from /lib/libglib-2.0.so.0
#6  0xb7f7336f in ?? () from /lib/libglib-2.0.so.0
#7  0xb7e9580e in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#8  0xb74427ee in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 2 (Thread 0xb69fcb70 (LWP 14891)):
#0  0xb7fe2430 in __kernel_vsyscall ()
#1  0xb7434ba6 in poll () from /lib/tls/i686/cmov/libc.so.6
#2  0xb6d869b2 in ?? () from /usr/lib/gstreamer-0.10/libgstalsa.so
#3  0xb7e02895 in ?? () from /usr/lib/libgstreamer-0.10.so.0
#4  0xb7e041a7 in ?? () from /usr/lib/libgstreamer-0.10.so.0
#5  0xb7f7499f in ?? () from /lib/libglib-2.0.so.0
#6  0xb7f7336f in ?? () from /lib/libglib-2.0.so.0
#7  0xb7e9580e in start_thread () from /lib/tls/i686/cmov/libpthread.so.0
#8  0xb74427ee in clone () from /lib/tls/i686/cmov/libc.so.6

Thread 1 (Thread 0xb7033930 (LWP 14887)):
#0  0xb7fe2430 in __kernel_vsyscall ()
#1  0xb7434ba6 in poll () from /lib/tls/i686/cmov/libc.so.6
#2  0xb7f5953b in g_poll () from /lib/libglib-2.0.so.0
#3  0xb7f4c55b in ?? () from /lib/libglib-2.0.so.0
#4  0xb7f4cb8f in g_main_loop_run () from /lib/libglib-2.0.so.0
#5  0x0804a26a in main (argc=1, argv=0xbffff354) at main.c:166
(gdb)