pyaudio - "Listen" until voice is detected and then record to a .wav file

I'm having some problems and I cannot seem to get my head around the concept.

What I am trying to do is this:

Have the microphone "listen" for voiced (above a particular threshold) and then start recording to a .wav file until the person has stopped speaking / the signal is no longer there. For example:

begin:
   listen() -> nothing is being said
   listen() -> nothing is being said
   listen() -> VOICED - _BEGIN RECORDING_
   listen() -> VOICED - _BEGIN RECORDING_
   listen() -> UNVOICED - _END RECORDING_
end

I want to do this also using "threading" so a thread would be created that "listens" to the file constantly, and, another thread will begin when there is voiced data.. But, I cannot for the life of me figure out how I should go about it.. Here is my code so far:

import wave
import sys
import threading
from array import array
from sys import byteorder

try:
    import pyaudio
    CHECK_PYLIB = True
except ImportError:
    CHECK_PYLIB = False

class Audio:
    _chunk = 0.0
    _format = 0.0
    _channels = 0.0
    _rate = 0.0
    record_for = 0.0
    stream = None

    p = None

    sample_width = None
    THRESHOLD = 500

    # initial constructor to accept params
    def __init__(self, chunk, format, channels, rate):
        #### set data-types

        self._chunk = chunk
        self.format = pyaudio.paInt16,
        self.channels = channels
        self.rate = rate

        self.p = pyaudio.PyAudio();

   def open(self):
       # print "opened"
       self.stream = self.p.open(format=pyaudio.paInt16,
                                 channels=2,
                                 rate=44100,
                                 input=True,
                                 frames_per_buffer=1024);
       return True

   def record(self):
       # create a new instance/thread to record the sound
       threading.Thread(target=self.listen).start();

   def is_silence(snd_data):
       return max(snd_data) < THRESHOLD

   def listen(self):
       r = array('h')

       while True:
           snd_data = array('h', self.stream.read(self._chunk))

           if byteorder == 'big':
               snd_data.byteswap()
           r.extend(snd_data)

       return sample_width, r

I'm guessing that I could record "5" second blocks, and, then if the block is deemed as "voiced" then it the thread should be started until all the voice data has been captured. However, because at current it's at while True: i don't want to capture all of the audio up until there are voiced commands, so e.g. "no voice", "no voice", "voice", "voice", "no voice", "no voice" i just want the "voice" inside the wav file.. Anyone have any suggestions?

Thank you

EDIT:

import wave
import sys
import time 
import threading 
from array import array
from sys import byteorder
from Queue import Queue, Full

import pyaudio 

CHUNK_SIZE = 1024
MIN_VOLUME = 500

BUF_MAX_SIZE = 1024 * 10 

process_g = 0 

def main():

stopped = threading.Event()

q = Queue(maxsize=int(round(BUF_MAX_SIZE / CHUNK_SIZE)))

listen_t = threading.Thread(target=listen, args=(stopped, q))

listen_t.start()

process_g = threading.Thread(target=process, args=(stopped, q))

process_g.start()

try:

    while True:
        listen_t.join(0.1)
        process_g.join(0.1)
except KeyboardInterrupt:
        stopped.set()

listen_t.join()
process_g.join()

  def process(stopped, q):

  while True:
    if stopped.wait(timeout = 0):
        break
    print "I'm processing.."
    time.sleep(300)

   def listen(stopped, q):

   stream = pyaudio.PyAudio().open(
        format = pyaudio.paInt16,
        channels = 2,
        rate = 44100,
        input = True,
        frames_per_buffer = 1024    
            )

     while True:

      if stopped and stopped.wait(timeout=0):
          break
      try:
        print process_g
        for i in range(0, int(44100 / 1024 * 5)):
            data_chunk = array('h', stream.read(CHUNK_SIZE))
            vol = max(data_chunk)
            if(vol >= MIN_VOLUME):
                print "WORDS.."
            else:
                print "Nothing.."

        except Full:
                pass 

    if __name__ == '__main__':
    main()

Now, after every 5 seconds, I need the "process" function to execute, and then process the data (time.delay(10) whilst it does this and then start the recording back up..

Look here:

https://github.com/jeysonmc/python-google-speech-scripts/blob/master/stt_google.py

It even converts Wav to flac and sends it to the google Speech api , just delete the stt_google_wav function if you dont need it ;)